Fix live migration api stuck when migrate to old nova node

Commit bc45c56f102cdef58840e02b609a89f5278e8cce disable instance
live migration between different verison node. If the two nodes
with different rpc version, will raise exception
LiveMigrationWithOldNovaNotSafe. But this exception didn't catch
as expected exception, that make the instance status stuck at
migrating. This patch add LiveMigrationWithOldNovaNotSafe as
expected exception.

Conflicts:
        nova/tests/unit/api/openstack/compute/contrib/test_admin_actions.py
        nova/tests/unit/api/openstack/compute/contrib/test_migrate_server.py
        nova/tests/unit/conductor/test_conductor.py

Change-Id: I1dcee9181fd0ef293628b30766112f00792796ab
Closes-Bug: #1377644
Merge "Fix live migration api stuck when migrate to old nova node" into stable/juno