Set device owner for health manager port
Set device owner for health manager port

Devstack plugin creates the health manager port with no device owner.
This is unusual as this value usually has some meaningful value, and
although the port name is quite descriptive, a distro could use the
device owner value to lookup the health manager port.

Closes-bug: #1592007
Change-Id: I8f75c5f70837dbc2f66d3e34c52a39a25614ada3

openstack/octavia,openstack/octavia,openstack/octavia