Fix live migration on Pike and later

The live_migration_uri was removed in
Ifea82dc03a859356eb55b097aa5747e3fa0c40ba since it is currently a
deprecated config option. However, nova has not adequately implemented
the replacement config vars for Pike, so the deprecated option must
be used to configure live migration with SSH settings[1].

The deprecated option can be removed once the nova bug is resolved.

This also pulls in the change from Ia389e78994da0f5f1cd99edeafeef13009906621
which is needed to perform SSH tunnelled migrations.

[1] https://bugs.launchpad.net/nova/+bug/1671288

Change-Id: I72d70d3621e5446c70008f6d680c7e315b05e150
(cherry picked from commit 12e09a3)

templates/nova.conf.j2

@@ -270,6 +270,8 @@ images_type = rbd
 images_rbd_pool = {{ nova_libvirt_images_rbd_pool }}
 images_rbd_ceph_conf = /etc/ceph/ceph.conf
 {% endif %}
+live_migration_uri = "qemu+ssh://nova@%s/system?no_verify=1&keyfile={{ nova_system_home_folder }}/.ssh/id_rsa"
+live_migration_tunnelled = True
 hw_disk_discard = {{ nova_libvirt_hw_disk_discard }}
 disk_cachemodes = {{ nova_libvirt_disk_cachemodes }}
 {% endif %}