decouple the mutual-dependence of config.py and server.py

decouple the mutual-dependence of config.py and server.py

Currently server.py relies on CONF while starting the service, and
config.py's config_fie is set in server.py, which is wrongly bi-depended
this patch aims to let Config parse the sys.argv personally,
just as oslo.config do, so that decouple the mutual-dependency

Change-Id: I46887d122a98d478caebe9eeb7ab038941ce1f6b
Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>