packaging: updated the upgrade to use engine 'maint' mode

* Updated the implementaion of the maintenance mode. Now
instead of starting the engine with different ports we use
the "real" maintenance mode provided by the engine and implemented
with the commit [1].

* Added a use of utility that checks the system and finds
zombie async tasks. If such tasks are found, we clean them,
including the related compensasions.

[1] SHA 9173096a1a6324045d13429ce9d704b7cc97d2ef
    Patch: http://gerrit.ovirt.org/#/c/8669
    Bug-URL: https://bugzilla.redhat.com/868639

Bug-Url: https://bugzilla.redhat.com/868642
Change-Id: Iad4fdd62493085b7ecb4d51fb54e8057418075e1
Signed-off-by: Alex Lourie <alourie@redhat.com>