engine : Introduction of DecoratedCommand

This patch introduces the DecoratedCommand class
that intercepts calls to endAction and calls
handleEndActionResult

Change-Id: I0ffe9899c324110502319078cf5fe16f3a4b8c11
Bug-Url: https://bugzilla.redhat.com/1083769
Signed-off-by: Ravi Nori <rnori@redhat.com>