Close connection with timedout slaves.
Close connection with timedout slaves.

Now masters, using the time at which the last REPLCONF ACK was received,
are able to explicitly disconnect slaves that are no longer responding.

Previously the only chance was to see a very long output buffer, that
was highly suboptimal.

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