Ignore empty PUTs in api-server and don't generate as such in client lib

[Hampapur Ajay]

If there is an empty PUT (i.e. put with no keys in the body json) api-server currently sends an update to rabbitmq anyways and this triggers a series of evaluations (update ifmap after read-from db, ifmap subscribers re-evaluating the object) that is inefficient.
In case of mis-behaving clients doing empty PUTs it adds unnecessary load on system.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/14215
Submitter: Hampapur Ajay (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/14215
Committed: http://github.org/Juniper/contrail-controller/commit/041c2b168880281da0abaff6e8f9166272915224
Submitter: Zuul
Branch: master

commit 041c2b168880281da0abaff6e8f9166272915224
Author: Hampapur Ajay <email address hidden>
Date: Fri Oct 2 12:23:14 2015 -0700

Ignore update request when nothing has changed in object.

In api client library, do not send update to server if none of the
attributes were updated. In api server, ignore PUTs when there is
no body or empty body.

Change-Id: Ia060380abb737c4ed7c869af15e23375f99fff41
Closes-Bug: #1502237