API: Add debug message for every API call
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

jay-lau/magnum,dimtruck/magnum,dimtruck/magnum,openstack/magnum,ArchiFleKs/magnum,ArchiFleKs/magnum,openstack/magnum