Use new dictGetRandomKeys() API to get samples for eviction.
Use new dictGetRandomKeys() API to get samples for eviction.

The eviction quality degradates a bit in my tests, but since the API is
faster, it allows to raise the number of samples, and overall is a win.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis