Allow neutron-sanity-check to check OVS patch port support

This patch allows to check OVS patch port support using:

  neutron-sanity-check --ovs_patch

or pass in the deployed configuration files with a non-empty
AGENT/tunnel_types (indeed patch ports are used to interconnect
br-int and br-tun):

  neutron-sanity-check --config-file ml2.conf.ini

DocImpact
Related-Bug: #1285335
Change-Id: Ic7bfabd1f4b85bfa490dd06c70eb5682ee42a681
Merge "Allow neutron-sanity-check to check OVS patch port support"