uphold the smove contract to return 0 when the element is not a member of the source set, even if source=dest

Originally, only the +slave event which occurs when a slave is
reconfigured during sentinelResetMasterAndChangeAddress triggers a flush
of the config to disk.  However, newly discovered slaves don't
apparently trigger this flush but do trigger the +slave event issuance.

So if you start up a sentinel, add a master, then add a slave to the
master (as a way to reproduce it) you'll see the +slave event issued,
but the sentinel config won't be updated with the known-slave entry.

This change makes sentinel do the flush of the config if a new slave is
deteted in sentinelRefreshInstanceInfo.

To rewrite the config in the loop that adds slaves back after a master
reset, in order to handle switching to another master, is useless: it
just adds latency since there is an fsync call in the inner loop,
without providing any additional guarantee, but the contrary, since if
after the first loop iteration the server crashes we end with just a
single slave entry losing all the other informations.

It is wiser to rewrite the config at the end when the full new
state is configured.

limit.

This fixes issue #2535, that was actually an hiredis library bug (I
submitted an issue and fix to the redis/hiredis repo as well).

When an asynchronous hiredis connection subscribes to a Pub/Sub channel
and gets an error, and in other related conditions, the function
redisProcessCallbacks() enters a code path where the link is
disconnected, however the function returns before freeing the allocated
reply object. This causes a memory leak. The memory leak was trivial to
trigger in Redis Sentinel, which uses hiredis, every time we tried to
subscribe to an instance that required a password, in case the Sentinel
was configured either with the wrong password or without password at
all. In this case, the -AUTH error caused the leaking code path to be
executed.

It was verified with Valgrind that after this change the leak no longer
happens in Sentinel with a misconfigured authentication password.

master was closing the connection if the RDB transfer took long time.
and also sent PINGs to the slave before it got the initial ACK, in which case the slave wouldn't be able to find the EOF marker.

Bug as old as Redis and blocking operations. It's hard to trigger since
only happens on instance role switch, but the results are quite bad
since an inconsistency between master and slave is created.

How to trigger the bug is a good description of the bug itself.

1. Client does "BLPOP mylist 0" in master.
2. Master is turned into slave, that replicates from New-Master.
3. Client does "LPUSH mylist foo" in New-Master.
4. New-Master propagates write to slave.
5. Slave receives the LPUSH, the blocked client get served.

Now Master "mylist" key has "foo", Slave "mylist" key is empty.

Highlights:

* At step "2" above, the client remains attached, basically escaping any
  check performed during command dispatch: read only slave, in that case.
* At step "5" the slave (that was the master), serves the blocked client
  consuming a list element, which is not consumed on the master side.

This scenario is technically likely to happen during failovers, however
since Redis Sentinel already disconnects clients using the CLIENT
command when changing the role of the instance, the bug is avoided in
Sentinel deployments.

Closes #2473.

Itereator misuse due to analyzeLatencyForEvent() accessing the
dictionary during the iteration, without the iterator being
reclared as safe.

--stat mode already used to reconnect automatically if the server is no
longer available. This is useful since this is an interactive mode used
for debugging, however the same applies to --latency and --latency-dist
modes, so now both use the reconnecting command execution as well.

The reconnection code was modified to use basic VT100 escape sequences
in order to play better with different kinds of output on the screen
when the reconnection happens, and to hide the reconnection attempt
output when finally the reconnection happens.

So far not able to find a color palette within the 256 colors which is
not confusing. However I believe it is a possible task, so will try
better later.

Still not happy with the result but low grays are hard to see in certain
monitors with a non perfect gamma.

This test on Linux was extremely slow, since in Tcl we can't enable
easily tcp-nodelay, so the busy loop used to take *a lot* with bigger
writes. Fixed using pipelining.

Code was adding '\n'  (line 521) to the end of NIL values exlusively making csv output inconsistent.  Removed '\n'

Rationale is that when re-entering, it is likely due to Lua debugging
hooks. Returning an error will be ignored in most cases, going totally
unnoticed. With the log at least we leave a trace.

Related to issue #2302.

Instead of calling redisPanic() to abort the server.

Related to issue #2302.

Related to issue #2302.

The cleanup code expects that if 'di' is not NULL, it is a valid
iterator that should be freed.

The result of this bug was a crash of the AOF rewriting process if an
error occurred after the DBs data are written and the iterator is no
longer valid.

This fix is from @NanXiao, however I was not able to retain authorship
because the Pull Request original repository was removed.

1. Server unxtime may remain not updated while loading AOF, so ETA is
not updated correctly.

2. Number of processed byte was not initialized.

3. Possible division by zero condition (likely cause of issue #1932).