DM: do not configure lo0 IP based on vtep IP

[amit surana]

Currently, DM configures interface lo0 IP on the MX based on the BGP router IP field of the BGP router object. In cases where evpn+vxlan is not needed (and so lo0 doesn't have to be the tunnel endpoint), the admin could desire to use a non-loopback interface as tunnel endpoint. This is not possible today because the commit fails due to the tunnel source-ip being present on lo0 (as pushed by DM) and another interface (which was already configured by the user). To support this, DM will not attempt to configure lo0 IP (user will have to do this step manually).

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/29866
Submitter: Suresh Balineni (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/29866
Committed: http://github.org/Juniper/contrail-controller/commit/8eed9ccaa401371f9bdec69497d88bcf1c29e201
Submitter: Zuul (<email address hidden>)
Branch: master

commit 8eed9ccaa401371f9bdec69497d88bcf1c29e201
Author: sbalineni <email address hidden>
Date: Fri Mar 24 11:42:12 2017 -0700

[DM]: Do not push lo0 config if no loopback ip is configured

- introduced new property in physical router: loopback_ip
- push lo0 interface config only if loopback_ip is configured in PR object
- use loopback_ip in-place of dataplane_ip if dataplane_ip is not configured
- added tests

Closes-Bug: #1675124

Change-Id: I38078d9d79655f96c3565a2741f0e41ba437c7bd