trunks: Made it possible to reinitialize AuthorizationSession

this commit allows us to call StartUnboundSession/StartBoundSession
multiple times in the same AuthorizationSession. This is useful because
session resources are now freed correctly when a session is
reinitialized.

BUG=None
TEST=unit and manual

Change-Id: I32f4ec6750719d9f6a402ec5f0b49484c76d60bf
Reviewed-on: https://chromium-review.googlesource.com/239200
Reviewed-by: Darren Krahn <dkrahn@chromium.org>
Commit-Queue: Utkarsh Sanghi <usanghi@chromium.org>
Tested-by: Utkarsh Sanghi <usanghi@chromium.org>
2 files changed