Add negative tests for VIF attach/detach operations

Add tests:
  test_vif_already_attached_on_internal_info
  test_vif_already_attached_with_portgroups
  test_vif_attach_no_free_port
  test_vif_attach_no_port
  test_vif_attach_with_empty_portgroup
  test_vif_attach_port_not_in_portgroup
  test_vif_attach_node_doesnt_exist
  test_vif_attach_no_args
  test_vif_detach_not_existing
  test_vif_detach_no_args

Closes-Bug: #1666534
Change-Id: I657fbecd37ceec424da6182507f324b653288857
1 file changed