Added support for the old queue behavior - limit the max queue size.

This fixed the following issues:
Zendesk#323 - MoH from Park Server unintelligible after 15 seconds
PT44534121 - Call Park music will stop playing after 15 secs

The old behavior, have a limited queue,  was needed because media components
from sipXpark relied on it, as media queues are usually full.

The queue can be limited or unlimited, the default is limited. Components
have the possibility to chose which kind of queue to use. As for this
moment the only component that is using a limited queue is sipXpark.
The other components are using an unlimited queue.

pprer
Fixed various issues indicated by Valgrind: - garbage collector thread is started on demand by user agent because otherwise it may start too soon and use uninitialized values; - garbage collector thread should be stopped on demand from user agent because otherwise it may be stopped after user agent was destroyed and use an invalid user agent; - fixed a race between thread creation and var initialization;
Merge commit 'tags/reorder_temp' into release-4.6
PT44358975: circular dependency in openacd beans
PT45579013 - Assertion in sipxpark on Ctrl+C

The assertion was happening in mongo cleanup code. It seems that mongo needs
some help to cleanup nicely and this is done by adding an explicit call to
mongo::dbexit(mongo::EXIT_CLEAN).

This was added in all components that were showing this assert: park, rls, saa.
Merge branch 'PT45579013' into release-4.6-unstable

Conflicts:
	sipXpark/src/main.cpp