Make app_queue and res_agi independent of AMI being enabled.

Make app_queue and res_agi independent of AMI being enabled.

The https://reviewboard.asterisk.org/r/2888/ review changes manager to not
subscribe to stasis when it is disabled for performance reasons.  When
manager is disabled app_queue and res_agi decline to load and fail to
clean up what they have already allocated.

* Made app_queue and res_agi clean up allocated resources when they
decline to load.

* Made app_queue and res_agi use their own subscriptions to the stasis
topics instead of borrowing manager's message router structure
inappropriately.

(closes issue ASTERISK-22604)
Reported by: rmudgett

Review: https://reviewboard.asterisk.org/r/2902/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@400671 65c4cc65-6c06-0410-ace0-fbb531ad65f3