Several stylistic fixes for tests related patch
https://review.openstack.org/#/c/52165/ .
* assign networks on interfaces only in case if node
  was added to cluster
* assigned networks should be only for one interface
* remove mac assignment in test, because
  it is done in _create_interfaces_from_meta

Change-Id: I8f34bc77ad450206d11fd4b7bff464d6f8c26f60
Merge "Several stylistic fixes for tests related patch https://review.openstack.org/#/c/52165/ . * assign networks on interfaces only in case if node   was added to cluster * assigned networks should be only for one interface * remove mac assignment in test, because   it is done in _create_interfaces_from_meta"