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.
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: added TODO items in 02 unit.
Sentinel test: add stub for unit 04.