Set root logger for all openstack services to WARNING

It seems that the separate loggers (like amqp, sqlalchemy, etc)
can only be more verbose than the root logger. So if root logger
has INFO level, it does not matter that [logger_sqlalchemy] has
level=WARNING set, it will still be using INFO level.

Closes-Bug: PROD-34250
Change-Id: I732a1284b2fa9992ffea044b2048d5ae251cfcf2
1 file changed