quark 500's on Gateway conflict, should return 400

[Kyle Haley]

When a neutron.common.exceptions.GatewayConflictWithAllocationPools exception is thrown, it results in a 500, but it should throw a 400 since this is a bad request, not a 500 error.

The exception is also consumed and not logged properly.

We need to catch the GatewayConflictWithAllocationPools exception and instead raise a BadRequest with the relevant information to the user.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/339210

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/339210
Committed: https://git.openstack.org/cgit/openstack/quark/commit/?id=203412773dac34fee430ffe2cc885f1830b408dc
Submitter: Jenkins
Branch: master

commit 203412773dac34fee430ffe2cc885f1830b408dc
Author: Kyle Haley <email address hidden>
Date: Thu Jul 7 12:56:26 2016 -0700

    Raise GatewayConflict as BadRequest

    neutron GatewayConflictWithAllocationPools exception is raised
    as a 500, but it is actually user error, so it should be a 400.
    Catch the GatewayConflictWithAllocationPools exception and raise
    as a BadRequest with the relevant info.

    Change-Id: Id94590c2c8637a64a90f06834c7e3400ea2b6330
    JIRA:NCP-1993
    Closes-Bug: #1599980