ensure that port is added to bridge after a reboot

This is a change to the interfaces file to allow
openvswitch to start the ovs-bridge and to add the
specified ports.  Without this change, the bridge
comes up after a reboot of the seed or undercloud,
but the port associated with the physical interface
doesn't come up.

Change-Id: Ic968f39b16934c9e55d9aa448cbd9de54f659d4d
Closes-Bug: 1373063
Co-Authored-By: Ashok kumaran B<ashokkumaran.b@hp.com>
Merge "ensure that port is added to bridge after a reboot"