* TLS: Session caching configuration support.
* TLS: Remove redundant config initialization.

* Tests: fix and reintroduce redis-cli tests.

These tests have been broken and disabled for 10 years now!

* TLS: add remaining redis-cli support.

This adds support for the redis-cli --pipe, --rdb and --replica options
previously unsupported in --tls mode.

* Fix writeConn().

Similarly to EXPIREAT with TTL in the past, which implicitly deletes the
key and return success, RESTORE should not store key that are already
expired into the db.
When used together with REPLACE it should emit a DEL to keyspace
notification and replication stream.

it to calculate hash, we should use newsds.

On some platforms strtold("+inf") with valgrind returns a non-inf result

[err]: INCRBYFLOAT does not allow NaN or Infinity in tests/unit/type/incr.tcl
Expected 'ERR*would produce*' to equal or match '1189731495357231765085759.....'

tests were sensitive to additional log lines appearing in the log
causing the search to come empty handed.

instead of just looking for the n last log lines, capture the log lines
before performing the action, and then search from that offset.

* tests/valgrind: don't use debug restart

DEBUG REATART causes two issues:
1. it uses execve which replaces the original process and valgrind doesn't
   have a chance to check for errors, so leaks go unreported.
2. valgrind report invalid calls to close() which we're unable to resolve.

So now the tests use restart_server mechanism in the tests, that terminates
the old server and starts a new one, new PID, but same stdout, stderr.

since the stderr can contain two or more valgrind report, it is not enough
to just check for the absence of leaks, we also need to check for some known
errors, we do both, and fail if we either find an error, or can't find a
report saying there are no leaks.

other changes:
- when killing a server that was already terminated we check for leaks too.
- adding DEBUG LEAK which was used to test it.
- adding --trace-children to valgrind, although no longer needed.
- since the stdout contains two or more runs, we need slightly different way
  of checking if the new process is up (explicitly looking for the new PID)
- move the code that handles --wait-server to happen earlier (before
  watching the startup message in the log), and serve the restarted server too.

* squashme - CR fixes

For example:
    BITOP not targetkey sourcekey

If targetkey and sourcekey doesn't exist, BITOP has no effect,
we do not propagate it, thus can save aof and replica flow.

And minor edits to README

cluster.c remove "if (nodeIsMaster(myself))" judgement before clusterSendFail in markNodeAsFailingIfNeeded, avoiding slave failover requires twice vote requests

updated copyright year to 2020

Changed "2015" to "2020"

EXEC always fails with EXECABORT and multi-state is cleared

In order to support the use of multi-exec in pipeline, it is important that
MULTI and EXEC are never rejected and it is easy for the client to know if the
connection is still in multi state.

It was easy to make sure MULTI and DISCARD never fail (done by previous
commits) since these only change the client state and don't do any actual
change in the server, but EXEC is a different story.

Since in the past, it was possible for clients to handle some EXEC errors and
retry the EXEC, we now can't affort to return any error on EXEC other than
EXECABORT, which now carries with it the real reason for the abort too.

Other fixes in this commit:
- Some checks that where performed at the time of queuing need to be re-
  validated when EXEC runs, for instance if the transaction contains writes
  commands, it needs to be aborted. there was one check that was already done
  in execCommand (-READONLY), but other checks where missing: -OOM, -MISCONF,
  -NOREPLICAS, -MASTERDOWN
- When a command is rejected by processCommand it was rejected with addReply,
  which was not recognized as an error in case the bad command came from the
  master. this will enable to count or MONITOR these errors in the future.
- make it easier for tests to create additional (non deferred) clients.
- add tests for the fixes of this commit.

fix memory leak in sentinel connection sharing

Fix comments in listpack.c

Inconsistent RDB saving when in Sentinel mode

- enforcing of SHUTDOWN_NOSAVE flag in one place to make it consitent
  when running in Sentinel mode

See #7401.

Related to #7387.