utils: Introduce CallbackChain

Added new utility class encapsulating the pattern
of invoking multiple alternative methods to achieve
given task.

Change-Id: I5b35eeb3c7865945458801d13615c5dc92ebb5dd
Signed-off-by: Martin Betak <mbetak@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/19228
Reviewed-by: Dan Kenigsberg <danken@redhat.com>