Changed 'json' to 'JSON'

Change-Id: Idac5c4850f8bb727e17967532ab0b9b9c8e99068
Some edits for help strings

Some edits for neutron help strings as noticed by Lana during review of
this patch:
https://review.openstack.org/#/c/102900/

Change-Id: I4f6cbb3ced85e15c5f4f716aad630090955de31b
Co-Authored-By: Lana Brindley <openstack@lanabrindley.com>
Add MacAddressInUseClient exception handling

Nova needs a specific client exception defined for the server's
MacAddressInUse exception when allocating ports so it can handle the
exception properly, otherwise the NeutronClientException with a 409 can
be confused with other errors.

Partial-Bug: #1347778

Change-Id: Ia02dbc8fe32a43adeb229e3b640b9b33ec0dd6c7
Merge "Add MacAddressInUseClient exception handling"
Merge "Changed 'json' to 'JSON'"
Merge "Some edits for help strings"