no debug message in REST API layer

[Eli Qiao]

Add debug message for every REST API call.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/243910
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=dc1dec5bd06e568bc1db28e545910ba98f5ebf36
Submitter: Jenkins
Branch: master

commit dc1dec5bd06e568bc1db28e545910ba98f5ebf36
Author: Eli Qiao <email address hidden>
Date: Sat Nov 14 23:02:10 2015 +0800

    API: Add debug message for every API call

    Added debug messages for each API call. It will helpful for debugging,
    especially on gate.

    This log message will be only print out when the request has body, and output
    will be like follows:

    Processing request: url: http://10.238.157.49:9511/v1/bays, POST, body:
    {"name": "k8s", "discovery_url": null, "master_count": 1, "baymodel_id":
    "e5534156-7b7d-4ddf-afe9-f4189a5e77fe", "node_count": "1",
    "bay_create_timeout": null}

    P.S. I would like to add it in routers, we'd better to LOG which controller
    is called, but since we are inherited from pecan, we don't want so much
    hacking to base class.

    Closes-Bug: #1516464
    Change-Id: I24543dfcb97a90b2849813ce7aaeb8904f7d50ca