Use patch ports to interconnect integration/physical bridges

Use by default patch ports to interconnect the integration to
physical bridges for the openvswitch agent in order to increase
performance.

For ovs/kernel without ovs patch port support on kernel side, veths
can be used through the new option OVS.use_veth_interconnection.

Patch port support can be tested using:

    neutron-sanity-check --ovs_patch

DocImpact
Closes-Bug: #1285335
Change-Id: I47106e57bf5b23891d7bf43815959e0d10156fba
Merge "Use patch ports to interconnect integration/physical bridges"