Use the correct configuration value for ovirt-3.3

During the backport in http://gerrit.ovirt.org/#/c/25022/ the name of a
configuration value has been improperly backported.
migration_progress_timeout does not yet exist for ovirt-3.3 and
migration_timeout should be used instead.

Change-Id: I9151ae1521a330f8e00ddf2f96d4b67888a0a7d6
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1078793
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/25929
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>