scope warnings to only display if the services are enabled

On my devstack environments I'm now always getting the Q_AGENT
warnings even though I don't have neutron enabled. This is mostly
confusing.

For these juno warnings lets just make sure that the whole thing
only prints out in the case where we've actually got that service
enabled.

Change-Id: I7d1bb2e65594c8bee2f572ca58a1b666e5d6caed
Merge "scope warnings to only display if the services are enabled"