Update libguestfs_backend to direct
Update libguestfs_backend to direct

RHOS-16 jobs fail at Images stage on below error, using direct
will fix this issue and also works for other releases

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1756120

Error:
| Monday 19 August 2019  20:11:17 +0000 (0:00:00.075)       0:03:13.789 *********
2019-08-19 20:11:19.738 | fatal: [undercloud-0]: FAILED! => {
2019-08-19 20:11:19.740 |     "changed": true,
2019-08-19 20:11:19.742 |     "cmd": [
2019-08-19 20:11:19.744 |         "virt-copy-in",
2019-08-19 20:11:19.746 |         "-a",
2019-08-19 20:11:19.748 |         "overcloud-full.qcow2",
2019-08-19 20:11:19.750 |         "/tmp/oc_repos/yum.repos.d",
2019-08-19 20:11:19.752 |         "/etc/"
2019-08-19 20:11:19.754 |     ],
2019-08-19 20:11:19.756 |     "delta": "0:00:00.299125",
2019-08-19 20:11:19.758 |     "end": "2019-08-19 16:11:19.338748",
2019-08-19 20:11:19.760 |     "rc": 1,
2019-08-19 20:11:19.762 |     "start": "2019-08-19 16:11:19.039623"
2019-08-19 20:11:19.764 | }
2019-08-19 20:11:19.766 |
2019-08-19 20:11:19.768 | STDERR:
2019-08-19 20:11:19.770 |
2019-08-19 20:11:19.772 | libvirt: XML-RPC error : Cannot recv data: Connection reset by peer
2019-08-19 20:11:19.774 | libguestfs: error: could not connect to libvirt (URI = qemu:///session):
Cannot recv data: Connection reset by peer [code=38 int1=104]

Change-Id: Icf5a78a9cf1a43af419207cda90fb336d209d655

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared