make jedis unit tests pass to Redis 2.8.1

* increase sentinel instance to test JedisSentinelTest
** clear() called, slave promoted to master (slave of no one), New
Sentinel force to restore it (demote) -> slave is not reusable
* ipv6 applied at Redis 2.8 -> localhost / 127.0.0.1 / ::1 is now all same

* Makefile: sleep some time for launch each sentinel (workaround to sentinel's issue)
** issue to sentinel leader vote: https://github.com/antirez/redis/issues/1419
*** sentinel may confused to vote with sentinels launched approximately same time