nova network dhcpbridge has direct DB access

[Hans Lindgren]

nova-network is currently broken due to direct DB access in dhcpbridge.

This issue was found using a multihost devstack setup where the non-controller node has an empty sql connection string.

[Openstack Gerrit (openstack-gerrit)]

Fix proposed to branch: master
Review: https://review.openstack.org/92086

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/92086
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=9b41af32bbbfc063eabf570fb95cdf516a8bb4a7
Submitter: Jenkins
Branch: master

commit 9b41af32bbbfc063eabf570fb95cdf516a8bb4a7
Author: Hans Lindgren <email address hidden>
Date: Mon May 5 12:30:18 2014 +0200

    Remove and block DB access in dhcpbridge

    This fixes an issue of direct DB access from happening in dhcpbridge
    by using an object method instead. For this to work and to prohibit
    future DB access from happening, the objects indirection API is set
    and DB access is blocked in a similar way to how it is done in
    nova-compute and nova-network.

    Change-Id: I5e3152aad13343a6a1ecd9b5b511429159c9d4c2
    Closes-Bug: #1316074