Move wait_for_interface_status into _check_interface

1.Move wait_for_interface_status into _check_interface.

2.In the case of test_reassign_port_between_servers, before check
iface['port_id'] and delete_interface, it is better to wait for the
status of port reach to active.

Change-Id: I9e185543da91d159709a2b773bab3945f4e79947
1 file changed