read_deleted snapshot and volume id mappings.

Since the migration that creates the volume_id_mappings and
snapshot_id_mappings tables does not populate the 'deleted' column,
queries to this table should not limit results to 'deleted=0'.
Limiting to non-deleted rows results in duplicate mappings being
created for existing instance mappings after an upgrade, and
throws off volume and snapshot ID to UUID mapping.

This is a stop-gap measure to ensure avoid serious breakage during
an upgrade.  The NULL columns in this table are actually unused
currently and can be populated in later grizzly migrations, if they
end up being used.

Fixes bug 1065785.

Change-Id: I893c994362a203288b9984f0ede24cbb274bfcc5
(cherry picked from commit 43bf834)

nova/db/sqlalchemy/api.py

@@ -2994,12 +2994,14 @@ def _volume_get_query(context, session=None, project_only=False):
 
 @require_context
 def _ec2_volume_get_query(context, session=None):
-    return model_query(context, models.VolumeIdMapping, session=session)
+    return model_query(context, models.VolumeIdMapping,
+                       session=session, read_deleted='yes')
 
 
 @require_context
 def _ec2_snapshot_get_query(context, session=None):
-    return model_query(context, models.SnapshotIdMapping, session=session)
+    return model_query(context, models.SnapshotIdMapping,
+                       session=session, read_deleted='yes')
 
 
 @require_context