There's a leak in the following scenario:
* AccurateClusterDuration is set to true.
* Add a few frames.
* An error is encountered while adding a frame and the
application bails without calling Cluster::Finalize
* All the frames we queues in QueueOrWriteFrames now leak.
This patch fixes this scenario by delete'ing any left over frames
in the Cluster's destructor.
Change-Id: I104f6814db18a86fae9877decfe6cc75b8937fcb
cbd676bb66