Implement import policy for the default RI of a VN

[Nischal Sheth]

It will be useful to have the ability to manipulate the attributes of IP
routes learnt via XMPP. Proposal is to do via import routing-policy(s)
applied on the VN.

ST will take the routing-policy(s) applied on the VN and link them to the
default RI for the VN. The expectation is that the existing code in CN
for processing policies on an RI should work without any modifications.
Note that this code was added to support import policy on the bookend RIs
of a service chain.

The schema already supports linkage between a RI and routing-policy. We
will need to add similar linkage between a VN and routing-policy.

As an example, such policies can be used to add communities to routes
based on matching the subnet prefix. These communities will automatically
get copied from the paths in the RI to the replicated VPN paths that are
advertised to other BGP peers using L3VPN NLRI.

UI changes for the same are tracked by bug 1743038.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/36187
Submitter: <email address hidden> (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/36187
Committed: http://github.com/Juniper/contrail-controller/commit/4d4d2b468d4fd77da91629e07bbc9848e96ebae4
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit 4d4d2b468d4fd77da91629e07bbc9848e96ebae4
Author: Sahil <email address hidden>
Date: Tue Oct 3 05:37:02 2017 -0700

[ST]: Modified to add rp and default RI link

1. Modified vnc_cfg schema to support linkage between a VN and routing
policy.
2. ST reads the routing policy from a VN and link it to VN's default RI.

Change-Id: Ic478d0aa5e430135b35e9776c6a1657c04992270
Closes-Bug: #1708045