Add migration code for updating lease status

Lease status was None before the status module was introduced.
This patch is for updating the None status.

Partially Implements: blueprint state-machine
Change-Id: I64cc07737d5c1c83a4f91d485a21c9a459305b9a

blazar/db/migration/alembic_migrations/versions/75a74e4539cb_update_lease_status.py

@@ -0,0 +1,43 @@
+# Copyright 2018 OpenStack Foundation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""update lease status
+
+Revision ID: 75a74e4539cb
+Revises: e66f199a5414
+Create Date: 2018-01-23 11:05:56.753579
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '75a74e4539cb'
+down_revision = 'e66f199a5414'
+
+from blazar.db import api as db_api
+from blazar.status import LeaseStatus as ls
+
+
+def upgrade():
+    leases = db_api.lease_get_all()
+    for lease in leases:
+        db_api.lease_update(lease['id'],
+                            {'status': ls.derive_stable_status(lease['id'])})
+
+
+def downgrade():
+    leases = db_api.lease_get_all()
+    for lease in leases:
+        db_api.lease_update(lease['id'],
+                            {'status': None})