Fix cluster.c inet_ntop use of sizeof(n->ip).
Fix cluster.c inet_ntop use of sizeof(n->ip).

Using sizeof with an array will only return expected results if the
array is created in the scope of the function where sizeof is used. This
commit changes the inet_ntop calls so that they use the fixed buffer
value as defined in redis.h which is 16.

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