Tracking request by adding request-id when logging

* Add request_id in context
* Logging out request_id in log file
* Put request_id in HTTP response headers

Change-Id: I779c9b6ef5aaa2f2a722b69a5d54d9696acb53c4
Extract all config entry in module: common.config

Change-Id: I1d749118bb2ed2b9d7873eae9db4a8ece436b082
Make create keystone user more graceful

Change-Id: Id3d5ffde0b42200b7ffe1e11dcc211b5bff2cb28
Reduce columns when do `postman list`

Change-Id: I29e1c3611f9e8bb7896ce69913cb5ed3eaf11452
Extract all openstack client into opsclient

Since balancer and node depend on novaclient/keystone, so extract the
openstack client code into one module. That is good for testing.

Change-Id: Id3acec45ba1d1341e848c272158a6f1e0dcb26ab
Support set config value in test cases.

Change-Id: Ib13cd5af94af247cddae672ac0bf47f31d12510e
Change default config example.

Change-Id: I40cfc9de570836cc697e9d548a7c980faa00a3b8
Add some tests for core balancer.

Change-Id: I1e187f0e5cac7ffa75f86db21d68aa4682d65bfa
Divide use_floating_ip_pool into two config.

Divide use_floating_ip_pool into two config: use_floating_ip, floating_ip_poo.

Change-Id: I223a90749d76c4a2aca8363136d3c61fca0ccc43
Fix type when get fixed-ip from instance.

Change-Id: I790ba249db23b3ee526202aee11865c8f825c9bb
Modify unified log output format

Modify unified log output format to match our specification.

Change-Id: I1bc61cf2a66b6f19339a3e93c69d386891d35be3