engine: Adjust host networks when cluster changes

When moving a host between clusters, the labeled host's
networks should be updated by the assignment of those
labeled network to the cluster:
- Cluster-assigned labeled networks should be configured
  on the hosts if a nic is labeled with those labels
- Labeled networks which were assigned to the host nics
  and not assigned to the target cluster should be removed
  from the host.

Change-Id: I5fa6e324c2833366a5fb34db9d2d754426dce316
Signed-off-by: Moti Asayag <masayag@redhat.com>