Move wait_for_interface_status from service client

wait_for_interface_status is used in test_attach_interfaces only
and the method is just a wrapper of sevice client method.
The service client module is not right place for the method.
Then this patch migrate the method to test_attach_interfaces.

Partially implements blueprint consistent-service-method-names

Change-Id: Ie6c05c83c6f029036f0ba105b6cdb82208616f38
2 files changed