db: rename_table is not a batch operation

This is reported upstream [1] but I suspect the root cause is that we
were relying on a bug in Alembic: renaming tables doesn't really make
sense as a batch operation, which by definition works by recreating
tables with an updated schema (to support SQLite and its lack of full
'ALTER' support).

[1] sqlalchemy/alembic#1453

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
Change-Id: I1da6d117778bbbad64b2df2dfd2f8aeef8a7084c

manila/db/migrations/alembic/versions/5077ffcc5f1c_add_share_instances.py

@@ -246,8 +246,9 @@ def upgrade_export_locations_table(connection):
     with op.batch_alter_table("share_export_locations") as batch_op:
         batch_op.drop_constraint('sel_id_fk', type_='foreignkey')
         batch_op.drop_column('share_id')
-        batch_op.rename_table('share_export_locations',
-                              'share_instance_export_locations')
+
+    op.rename_table(
+        'share_export_locations', 'share_instance_export_locations')
 
 
 def downgrade_export_locations_table(connection):