Allow host addresses allocated for service VMs to be filtered

[Nischal Sheth]

Consider a left VN/VPN and right VN/VPN with a SFC applied via a policy.
A /32 IP address is allocated for both interfaces of each service VM that
is spawned between the left and right VNs. These get re-originated in
other VN i.e. the /32s for the left interface get re-originated into the
right VN and vice-versa. It's desirable to filter these /32 routes and
prevent them from getting advertised into the other VN. It's also useful
to prevent these /32s from the left/right VNs from getting into left/right
VPNs as well.

Same with /128s in case of service chaining for IPv6.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/39056
Submitter: Nipa Kumar (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/39056
Committed: http://github.com/Juniper/contrail-specs/commit/150a2bf2b2d783deea23d514af0dcf29231c8740
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit 150a2bf2b2d783deea23d514af0dcf29231c8740
Author: Nipa Kumar <email address hidden>
Date: Fri Jan 19 10:37:28 2018 -0800

Enhanced Routing Policies to be applicable for interface-routes and static-routes

https://blueprints.launchpad.net/opencontrail/+spec/enhanced-routing-policies

Change-Id: Ifffed4501d6c5a0200f8945e7fbeed49079bc582
Partial-Bug: #1559811