Handle AggregateNotFound when deleting aggregate
Handle AggregateNotFound when deleting aggregate

If an error occurs during lease create and an aggregate isn't created,
an exception will be raised in cleanup_resources when trying to delete
the missing aggregate. Handle this gracefully and continue.

Closes-Bug: #1938241

Change-Id: I866bc7c369fb390f8c9204e36c06fadea17f6dd5

ChameleonCloud/blazar,openstack/blazar,ChameleonCloud/blazar,openstack/blazar