config: Treat ref-update ADD to existing ref as change

[Hampapur Ajay]

If a ref-update API is done on an object to an existing ref, the existing ref was not treated as such and type-specific handlers see it as a list instead of set.

So e.g if VN-1 refers to IPAM-1 with [1.1.1.0/28] subnet, on update VN-1 to IPAM-1 with [1.1.1.0/28, 2.2.2.0/28] subnets, the type-specific handlers saw VN-1 having 3 subnets [1.1.1.0/28, 1.1.1.0/28, 2.2.2.0/28] and complains of overlap

cfgm_common.exceptions.BadRequest: Overlapping addresses: [IPNetwork('1.1.1.0/28'), IPNetwork('1.1.1.0/28')]

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/24959
Submitter: Hampapur Ajay (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/24959
Committed: http://github.org/Juniper/contrail-controller/commit/648923cb6c0abc4aaeabe1d3a4021b900e918577
Submitter: Zuul
Branch: master

commit 648923cb6c0abc4aaeabe1d3a4021b900e918577
Author: Hampapur Ajay <email address hidden>
Date: Tue Oct 11 15:54:55 2016 -0700

For a ref-update ADD to an existing ref, treat it as change
possibly with attr.

Closes-Bug: 1634301
Change-Id: If55ec910fb942c8c39db9deec41980caf347d6a0