Bug 6969 - Memory leak during bundle tree restart

Bug 6969 - Memory leak during bundle tree restart

There are two root causes for that memory leak:

-  Retention on BlueprintContainer when desotrying them before "quiescing"
them:
Restarting a set of bundles requires cooperation between them to avoid
having retention on services due to on-going call, processing.
As OSGi APIs don't provide such functionality, the Quiesce APIs where
created, ensuring all calls to be finished before actually shutting down
the bundle. Once the set of bundles are quiesced, e.g. shut down, they
can safely be destroyed.

- Retention on the TopoProcessingProviderImpl due to unreleased resources:
https://git.opendaylight.org/gerrit/#/c/48283/

Change-Id: I0af4a27ac7c87f1cc158313f0497158733a045a5
Signed-off-by: Alexis de Talhouët <adetalhouet@inocybe.com>