Stasis: Fix potential memory leak of control data.

When queuing tasks onto the Stasis control queue, you can pass an
arbitrary data pointer and a function to free that data. All ARI
commands that use the Stasis control queue made the assumption that the
destructor function would be called in all paths, whether the task was
queued successfully or not. However, this was not correct. If a task was
queued onto a control structure that was already completed, the
allocated data would not be freed properly.

This patch corrects this by making sure that all return paths call the
data destructor.

Change-Id: Ibf06522094f8e5c4cce652537dc5d7222b1c4fcb