Refresh good slaves count after CONFIG SET min-slaves-...

This way just after the CONFIG SET enabling the min-slaves feature it is
possible to write to the database without delays.

src/config.c

@@ -797,10 +797,12 @@ void configSetCommand(redisClient *c) {
         if (getLongLongFromObject(o,&ll) == REDIS_ERR ||
             ll < 0) goto badfmt;
         server.repl_min_slaves_to_write = ll;
+        refreshGoodSlavesCount();
     } else if (!strcasecmp(c->argv[2]->ptr,"min-slaves-max-lag")) {
         if (getLongLongFromObject(o,&ll) == REDIS_ERR ||
             ll < 0) goto badfmt;
         server.repl_min_slaves_max_lag = ll;
+        refreshGoodSlavesCount();
     } else {
         addReplyErrorFormat(c,"Unsupported CONFIG parameter: %s",
             (char*)c->argv[2]->ptr);