Big Switch: hash shouldn't be updated on unsuccessful calls

[Kevin Benton]

The configuration hash db is updated on every response from the backend including errors that contain an empty hash. This is causing the hash to be wiped out if a standby controller is contacted first, which opens a narrow time window where the backend could become out of sync. It should only update the hash on successful REST calls.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/109695

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/109695
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=b8cf45218714937681d7df2e5b9d7d440cb2edd9
Submitter: Jenkins
Branch: master

commit b8cf45218714937681d7df2e5b9d7d440cb2edd9
Author: Kevin Benton <email address hidden>
Date: Fri Jul 25 12:25:39 2014 -0700

    Big Switch: Only update hash header on success

    This patch moves the hash update call into the success block
    of the server manager so the database isn't updated with
    a hash header from an error response. Additionally, it prevents
    the hash from being updated to an empty value if the hash header
    is not present in the response.

    Closes-Bug: #1348766
    Change-Id: I512d01f9bb91b208dd58883d2464951ecc6748e1

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/icehouse
Review: https://review.openstack.org/112059

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/112059
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=af2cc98f38b0efb7c52df8e363b876f285ccbb68
Submitter: Jenkins
Branch: stable/icehouse

commit af2cc98f38b0efb7c52df8e363b876f285ccbb68
Author: Kevin Benton <email address hidden>
Date: Fri Jul 25 12:25:39 2014 -0700

    Big Switch: Only update hash header on success

    This patch moves the hash update call into the success block
    of the server manager so the database isn't updated with
    a hash header from an error response. Additionally, it prevents
    the hash from being updated to an empty value if the hash header
    is not present in the response.

    Conflicts:

     neutron/tests/unit/bigswitch/test_servermanager.py

    Closes-Bug: #1348766
    Change-Id: I512d01f9bb91b208dd58883d2464951ecc6748e1
    (cherry picked from commit b8cf45218714937681d7df2e5b9d7d440cb2edd9)