Sentinel test: restart_instance should refresh pid attrib.

Also kill_instance was modified to warn when a test will try to kill the
same instance multiple times for error.
Sentinel test: test majority crashing Sentinels.

The test was previously performed by removing the master from the
Sentinel monitored masters. The test with the Sentinels crashed is
more similar to real-world partitions / failures.
Sentinel test: jump to next unit on test failure.

Sentinel tests are designed to be dependent on the previous tests in the
same unit, so usually we can't continue with the next test in the same
unit if a previous test failed.
Sentinel test: restart instances left killed by previous unit.

An unit can abort in the middle for an error. The next unit should not
assume that the instances are in a clean state, and must restart what
was left killed.
redis-cli: added comments to split program in parts.
redis-cli: --intrinsic-latency run mode added.
redis-cli: check argument existence for --pattern.
redis-cli: don't use uint64_t where actually not needed.

The computation is just something to take the CPU busy, no need to use a
specific type. Since stdint.h was not included this prevented
compilation on certain systems.
redis-cli: also remove useless uint8_t.
Sentinel test: kill masters instead of using DEBUG SLEEP in all tests.
Update --bigkeys to use SCAN

This commit changes the findBigKeys() function in redis-cli.c to use the new
SCAN command for iterating the keyspace, rather than RANDOMKEY.  Because we
can know when we're done using SCAN, it will exit after exhausting the keyspace.
Sentinel test: check role at end of unit 01.
Merge branch 'bigkeys_scan' of git://github.com/michael-grunder/redis into unstable
Sentinel test: added TODO items in 02 unit.
Sentinel test: add stub for unit 04.
Fix IP representation in clusterMsgDataGossip
Merge pull request #1565 from mattsta/fix-cluster-ipv6-addr

Fix IP representation in clusterMsgDataGossip
Fix misaligned word access in redisPopcount().
BITCOUNT fuzzy test with random start/end added.

It was verified in practice that this test is able to stress much more
the implementation by introducing errors that were only trivially to
detect with different offsets but impossible to detect starting always
at zero and counting bits the full length of the string.
Added two more BITCOUNT tests stressing misaligned access.