ACL: return error when removing a non existing password.
ACL: return error when removing a non existing password.

Otherwise it's very simple for an human mistake to think a password is
removed because of a typo in the ACL SETUSER myuser <somepass command
line.

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