Redis [NEW] When creating connections by redis-benchmark Idle mode, AUTH should be executed if -a para is present

Description of the feature

Currently, the idle mode of redis-benchmark just open N connections and waits, and -a para is ignored.

If -a para is present, the user wants to create N authenticated connections

Comment From: judeng

I'm not understand, why idle client need to send auth command. IMO this is pointless becease idle client will never send any requests. Or can you share your detailed test scenario?