Redis Disable WARNING about overcommit_memory if background save is disbled

As the title states, if save "" is set in the configuration file, overcommit_memory warning should be removed.

Comment From: oranagra

there are a few other mechanisms in redis using fork, specifically AOFRW, Replication, and even some modules. maybe if you just wanna suppress the warning explicitly we can add it to the ignore-warnings config. but if you want it to happen automatically depending on other configs, i don't think that's possible. first because the save confg can change and BGSAVE can be used after startup. but also because of replication (can't predict if it's gonna be used or not)