The db.api module provides a useless indirection to the only
implementation we ever had, sqlalchemy. Let's use that directly instead
of the wrapper.
Change-Id: I80353cfed801b95571523515fd3228eae45c96ae
Check the snapshot belongs to stack when deleting and showing
stack's snapshot, and restoring from snapshot.
Change-Id: I8ce170b40b05ae17669524d75f80e06e39986673
Closes-Bug: #1437602
In Heat objects, the default value of nullable attribute is
set in many of the object's fields, which is not required
as oslo object Field defines nullable as False by default
Change-Id: I0164b64c043816f624aeba19561a4a5f8d36689d
Closes-bug: #1439957
Thomas Herve