packaging: engine-backup: Log tar creation failures
packaging: engine-backup: Log tar creation failures

Bug-Url: https://bugzilla.redhat.com/1282397
Change-Id: I39df58b46fff2e34b04a3d6255bc265006c94031
Signed-off-by: Yedidyah Bar David <e7f2f616ce8817ad893bbeaad3e942e94c69d323@redhat.com>

zerodengxinchao/ovirt-engine,walteryang47/ovirt-engine,yapengsong/ovirt-engine,zerodengxinchao/ovirt-engine,yingyun001/ovirt-engine,eayun/ovirt-engine,yingyun001/ovirt-engine,yapengsong/ovirt-engine,yingyun001/ovirt-engine,yingyun001/ovirt-engine,walteryang47/ovirt-engine,eayun/ovirt-engine,eayun/ovirt-engine,yapengsong/ovirt-engine,walteryang47/ovirt-engine,zerodengxinchao/ovirt-engine,zerodengxinchao/ovirt-engine,eayun/ovirt-engine,yingyun001/ovirt-engine,walteryang47/ovirt-engine,zerodengxinchao/ovirt-engine,eayun/ovirt-engine,walteryang47/ovirt-engine,yapengsong/ovirt-engine,yapengsong/ovirt-engine