Remove a redundant wait_for_backup_deletion()

The rest_client module has a basic function wait_for_resource_deletion()
and it is enough to implement a small function is_resource_deleted()
in each service client for the same function.
This patch removes the wait_for_backup_deletion() and implement the
is_resource_deleted() for the code cleanup.

Partially implements blueprint consistent-service-method-names

Change-Id: I7c07f1cdde86be850f50825db01eb35c62497820

tempest/api/volume/admin/test_volumes_backup.py

@@ -43,7 +43,7 @@ class VolumesBackupsAdminV2Test(base.BaseVolumeAdminTest):
 
     def _delete_backup(self, backup_id):
         self.admin_backups_client.delete_backup(backup_id)
-        self.admin_backups_client.wait_for_backup_deletion(backup_id)
+        self.admin_backups_client.wait_for_resource_deletion(backup_id)
 
     def _decode_url(self, backup_url):
         return json.loads(base64.decodestring(backup_url))

tempest/services/volume/base/base_backups_client.py

@@ -116,14 +116,9 @@ class BaseBackupsClient(rest_client.RestClient):
                             self.build_timeout))
                 raise exceptions.TimeoutException(message)
 
-    def wait_for_backup_deletion(self, backup_id):
-        """Waits for backup deletion"""
-        start_time = int(time.time())
-        while True:
-            try:
-                self.show_backup(backup_id)
-            except lib_exc.NotFound:
-                return
-            if int(time.time()) - start_time >= self.build_timeout:
-                raise exceptions.TimeoutException
-            time.sleep(self.build_interval)
+    def is_resource_deleted(self, id):
+        try:
+            self.show_backup(id)
+        except lib_exc.NotFound:
+            return True
+        return False