Unity: temp snapshot for backup deleted twice

Remove the codes in `create/remove_export_snapshot`. The code there
is designed for mounting snapshots for remotefs filesystems. It is
unnecessary in Unity.

Change-Id: Ib2dcba29ca4d97f77501fd0068499aad09984ad6
Closes-bug: 1701311
(cherry picked from commit 3f53833)
(cherry picked from commit e4b41eb21e88e4af81e1f44cc70787af1ce5557b)

Author: Murray-LIANG

cinder/tests/unit/volume/drivers/dell_emc/unity/test_driver.py

@@ -245,17 +245,6 @@ def test_unmanage(self):
     def test_backup_use_temp_snapshot(self):
         self.assertTrue(self.driver.backup_use_temp_snapshot())
 
-    def test_create_export_snapshot(self):
-        snapshot = self.driver.create_export_snapshot(self.get_context(),
-                                                      self.get_snapshot(),
-                                                      self.get_connector())
-        self.assertTrue(snapshot.exists)
-
-    def test_remove_export_snapshot(self):
-        snapshot = self.get_snapshot()
-        self.driver.remove_export_snapshot(self.get_context(), snapshot)
-        self.assertFalse(snapshot.exists)
-
     def test_initialize_connection_snapshot(self):
         snapshot = self.get_snapshot()
         conn_info = self.driver.initialize_connection_snapshot(

cinder/volume/drivers/dell_emc/unity/driver.py

@@ -51,9 +51,10 @@ class UnityDriver(driver.TransferVD,
     Version history:
         00.05.00 - Initial version
         00.05.01 - Backport thin clone from Pike
+        00.05.02 - Fixed bug 170311: temp snapshot for backup was deleted twice
     """
 
-    VERSION = '00.05.01'
+    VERSION = '00.05.02'
     VENDOR = 'Dell EMC'
     # ThirdPartySystems wiki page
     CI_WIKI_NAME = "EMC_UNITY_CI"
@@ -207,12 +208,18 @@ def backup_use_temp_snapshot(self):
         return True
 
     def create_export_snapshot(self, context, snapshot, connector):
-        """Creates the snapshot for backup."""
-        return self.adapter.create_snapshot(snapshot)
+        """Creates the mount point of the snapshot for backup.
+
+        Not necessary to create on Unity.
+        """
+        pass
 
     def remove_export_snapshot(self, context, snapshot):
-        """Deletes the snapshot for backup."""
-        self.adapter.delete_snapshot(snapshot)
+        """Deletes the mount point the snapshot for backup.
+
+        Not necessary to create on Unity.
+        """
+        pass
 
     def initialize_connection_snapshot(self, snapshot, connector, **kwargs):
         return self.adapter.initialize_connection_snapshot(snapshot, connector)