Always wait for keystone haproxy backends

We wait for haproxy backend only for nova-network case, but neutron case
*does* rely on keystone as well. If we don't wait for keystone haproxy
backends, we could end up with neutron net-list failures.

Closes-bug: #1394140

Change-Id: I951f77cf5216c185756c4f430eb078df00319de2
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Merge "Always wait for keystone haproxy backends" into stable/5.1