Refactor: action executor: fetch session based on execution context

Refactor: action executor: fetch session based on execution context

There is little reason to fetch the session by name if at that point in
the action execution code path the id of the session is available.

Session that are in destroyed state are ignored. This simplify a bit the
overall execution flow.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I4a104e3b509c36b0ceea6e01f9dbd043ceb812b1