Removing wrapper method for "wait_for_volume_status" function

The wait_for_volume_status method in the base_volumes_client.py file is
a wrapper method that just uses the waiters.wait_for_volume_status function.
The wait_for_volume_status method is not a service method and that is why
it should be removed and the waiters.wait_for_volume_status function should
be used instead.

Partially implements blueprint consistent-service-method-names

Change-Id: I4516a2cc2dd6ada8d0a49392a98b949edc09a9fd
diff --git a/tempest/api/compute/volumes/test_attach_volume.py b/tempest/api/compute/volumes/test_attach_volume.py
index 01a8e58..e9c8e30 100644
--- a/tempest/api/compute/volumes/test_attach_volume.py
+++ b/tempest/api/compute/volumes/test_attach_volume.py
@@ -52,7 +52,8 @@
     def _detach(self, server_id, volume_id):
         if self.attachment:
             self.servers_client.detach_volume(server_id, volume_id)
-            self.volumes_client.wait_for_volume_status(volume_id, 'available')
+            waiters.wait_for_volume_status(self.volumes_client,
+                                           volume_id, 'available')
 
     def _delete_volume(self):
         # Delete the created Volumes
@@ -77,15 +78,16 @@
         self.volume = self.volumes_client.create_volume(
             size=CONF.volume.volume_size, display_name='test')['volume']
         self.addCleanup(self._delete_volume)
-        self.volumes_client.wait_for_volume_status(self.volume['id'],
-                                                   'available')
+        waiters.wait_for_volume_status(self.volumes_client,
+                                       self.volume['id'], 'available')
 
         # Attach the volume to the server
         self.attachment = self.servers_client.attach_volume(
             self.server['id'],
             volumeId=self.volume['id'],
             device='/dev/%s' % self.device)['volumeAttachment']
-        self.volumes_client.wait_for_volume_status(self.volume['id'], 'in-use')
+        waiters.wait_for_volume_status(self.volumes_client,
+                                       self.volume['id'], 'in-use')
 
         self.addCleanup(self._detach, self.server['id'], self.volume['id'])