Fixes valgrind error:
Syscall param write(buf) points to uninitialised byte(s)
   at 0x514C35D: ??? (syscall-template.S:81)
   by 0x456B81: clusterWriteHandler (cluster.c:1907)
   by 0x41D596: aeProcessEvents (ae.c:416)
   by 0x41D8EA: aeMain (ae.c:455)
   by 0x41A84B: main (redis.c:3832)
 Address 0x5f268e2 is 2,274 bytes inside a block of size 8,192 alloc'd
   at 0x4932D1: je_realloc (jemalloc.c:1297)
   by 0x428185: zrealloc (zmalloc.c:162)
   by 0x4269E0: sdsMakeRoomFor.part.0 (sds.c:142)
   by 0x426CD7: sdscatlen (sds.c:251)
   by 0x4579E7: clusterSendMessage (cluster.c:1995)
   by 0x45805A: clusterSendPing (cluster.c:2140)
   by 0x45BB03: clusterCron (cluster.c:2944)
   by 0x423344: serverCron (redis.c:1239)
   by 0x41D6CD: aeProcessEvents (ae.c:311)
   by 0x41D8EA: aeMain (ae.c:455)
   by 0x41A84B: main (redis.c:3832)
 Uninitialised value was created by a stack allocation
   at 0x457810: nodeUpdateAddressIfNeeded (cluster.c:1236)

Otherwise kill_instance + restart_instance in short succession will
still find the port busy and will fail.

Related to issue #2289.

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error occurred after the DBs data are written and the iterator is no
longer valid.

In order to avoid that misconfigured cluster nodes at some time may
force an IP update on other nodes, it is required that nodes update
their own address only on MEET messages. However it does not make sense
to do this the first time a node is contacted and yet does not have an
IP, we just risk that myself->ip remains not assigned if there are
messages lost or cluster creation procedures that don't make sure
everybody is targeted by at least one incoming MEET message.

Also fix the logging of the IP switch avoiding the :-1 tail.

Also explicitly set version to 0, add a protocol version define, improve
comments in the gossip structure.

Note that the structure layout is the same after the change, we are just
making the padding explicit with an additional not used 16 bits field.
So this commit is still able to talk with the previous versions of
cluster nodes.

Valgrind checks that the buffers we transfer via syscalls are all
composed of bytes actually initialized. This is useful, it makes we able
to avoid leaking informations in non initialized parts fo messages
transferred to other hosts. This commit fixes one of such issues.

Can't be initialized by resetManualFailover() since it's actual state
the function uses, so we need to initialize it at startup time. Not
really a bug in practical terms, but showed up into valgrind and is not
technically correct anyway.

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

Before this commit scripts were able to access / create keys outside the
set of hash slots served by the local node.

Under certain conditions the node list wasn't being fully populated
and 'create' would fail trying to call methods on nil objects.

This tiny bit of code has gone through so many revisions.  Hopefully
it's more correct now.

Fixes #2204

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).

Fixes issue #2225.

If we woke up to accept a connection, but we can't
accept it, inform the user of the error going on
with their networking.

(The previous message was the same for success or error!)

Otherwise there are security risks, especially when providing Redis as a
service, the user may "sniff" for admin commands renamed to an
unguessable string via rename-command in redis.conf.

The old list did not made much sense... and the flag is currently not
used at all, so no side effects.

It fixes a bad bug that crashes the server in certain conditions
as shown in issue #2210.

Related to #2094.