Remove wait_for_server_status from servers_client

wait_for_server_status of compute client just calls the one of waiters
module and the method is a wrapper.
So the method seems redundant and it doesn't fit as service clients.

This patch removes wait_for_server_status from compute client and
replaces it with waiters' one.

Partially implements blueprint consistent-service-method-names

Change-Id: Ie821ea4ba0924b71caba80132e1c383fb5bb125d
diff --git a/tempest/api/compute/base.py b/tempest/api/compute/base.py
index ea8e112..37c1e0a 100644
--- a/tempest/api/compute/base.py
+++ b/tempest/api/compute/base.py
@@ -144,8 +144,8 @@
         """
         if getattr(cls, 'server_id', None) is not None:
             try:
-                cls.servers_client.wait_for_server_status(cls.server_id,
-                                                          'ACTIVE')
+                waiters.wait_for_server_status(cls.servers_client,
+                                               cls.server_id, 'ACTIVE')
             except Exception as exc:
                 LOG.exception(exc)
                 cls.servers_client.delete_server(cls.server_id)
@@ -289,8 +289,8 @@
 
             if kwargs['wait_until'] == 'ACTIVE':
                 if kwargs.get('wait_for_server', True):
-                    cls.servers_client.wait_for_server_status(server_id,
-                                                              'ACTIVE')
+                    waiters.wait_for_server_status(cls.servers_client,
+                                                   server_id, 'ACTIVE')
         return image
 
     @classmethod