user can do add operation when update a cluster

[Eli Qiao]

currently seems we only support node_count when update cluster, I try add/replace , they are acted as same behavior.

so I can try this:

taget@taget-ThinkStation-P300:~/devstack$ magnum bay-list
+--------------------------------------+---------------+------------+--------------+-----------------+
| uuid | name | node_count | master_count | status |
+--------------------------------------+---------------+------------+--------------+-----------------+
| 71d00b0e-9325-4d5c-b6f5-0b644bd16023 | swarmbay-1 | 2 | 1 | UPDATE_COMPLETE |
| cac24024-13ab-4a24-b16d-19a8ad431afc | k8s-proxy-new | 1 | 1 | CREATE_COMPLETE |
+--------------------------------------+---------------+------------+--------------+-----------------+
taget@taget-ThinkStation-P300:~/devstack$ magnum --debug bay-update swarmbay-1 add node_count=1

seems we need to deny this operation.

if that attr has been exist, reminder user to use op=replace will make more sense.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/239200

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/239200
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=98371e52d4df78f7bbfcefc19bc323c076d6c3cf
Submitter: Jenkins
Branch: master

commit 98371e52d4df78f7bbfcefc19bc323c076d6c3cf
Author: Eli Qiao <email address hidden>
Date: Sun Oct 25 08:21:02 2015 +0800

    Raise exception when adding an existed attribute while update bay

    This patch raises a reasonable ClientSideError exception when adding
    an existed attribute while doing update bay.

    Besides, several apply_jsonpatch unit test cased added.
    Remove all related add_(existed) attr case of api side.

    Closes-Bug: #1509656
    Change-Id: Ifb0c8c7ca6cfe44481a436b9a8bbdb9143bb6d94