Reserve 3 migrations for DB backports

Reserve 3 migrations in case we need to backport changes to the
stable/rocky branch. Since there have not been as many DB changes as the
past, only reserving 3 instead of our conventional 5.

Change-Id: I065b9445547f6e8e1d3732ffd76ca7ddcbc9cfc6
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

cinder/db/sqlalchemy/migrate_repo/versions/124_placeholder.py

@@ -0,0 +1,22 @@
+#    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.
+
+# This is a placeholder for Rocky backports.
+# Do not use this number for new Stein work. New work starts after all the
+# placeholders.
+#
+# See this for more information:
+# http://lists.openstack.org/pipermail/openstack-dev/2013-March/006827.html
+
+
+def upgrade(migrate_engine):
+    pass

cinder/db/sqlalchemy/migrate_repo/versions/125_placeholder.py

@@ -0,0 +1,22 @@
+#    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.
+
+# This is a placeholder for Rocky backports.
+# Do not use this number for new Stein work. New work starts after all the
+# placeholders.
+#
+# See this for more information:
+# http://lists.openstack.org/pipermail/openstack-dev/2013-March/006827.html
+
+
+def upgrade(migrate_engine):
+    pass

cinder/db/sqlalchemy/migrate_repo/versions/126_placeholder.py

@@ -0,0 +1,22 @@
+#    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.
+
+# This is a placeholder for Rocky backports.
+# Do not use this number for new Stein work. New work starts after all the
+# placeholders.
+#
+# See this for more information:
+# http://lists.openstack.org/pipermail/openstack-dev/2013-March/006827.html
+
+
+def upgrade(migrate_engine):
+    pass