Delete events fails in postgres

[Zhang Yang]

An error happens when heat delete events in postgres, and you can find this error message in log, "Only deletion via a single table query is currently supported". It seems that JOIN/DELETE is not supported in "sqlalchemy/orm/". This error will breake almost all stack actions.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/85982

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/85982
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=dca6c7b6661d6b972fc9f783051227d2eb849d02
Submitter: Jenkins
Branch: master

commit dca6c7b6661d6b972fc9f783051227d2eb849d02
Author: Zhang Yang <email address hidden>
Date: Tue Apr 8 01:48:07 2014 -0700

    Fix delete event error in postgres

    An error happens when heat delete events in postgres,
     It seems that JOIN/DELETE is not supported in
    "sqlalchemy/orm/".

    Let heat delete events in postgres in the common
    way.

    Closes-Bug: #1301827
    Change-Id: Id320abf15c4fd9f58e411ad7de7f044a9b5d1c1e