Bugfix missing quantum-ovs-cleanup on startup

Ubuntu PPA packages are missing quantum-ovs-cleanup
service scripts whereas RHEL et al set this service up
appropriately on package installation.

This update addresses the missing service by installing
the upstart configuration and setting it to start at the
appropriate point in the bootup process, prior to the
l3 agent and dhcp agents.

For additional details, see:
https://bugs.launchpad.net/openstack-manuals/+bug/1156861

Change-Id: Id8abcc07ad3c0b0cfd742886a2f3d71d16585d91
Fixes-Bug: #1266495