do not add save parameter during config rewrite in sentinel mode (#7945)
do not add save parameter during config rewrite in sentinel mode (#7945)

Previous code would have added default redis save parameters
to the config file on rewrite, which would have been silently ignored
when the config file is loaded.

The new code avoids adding this, and also actively removes these lines
If added by a previous config rewrite. 
JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis