log module has nova specific default settings

[yong sheng gong]

log_opts = [
    cfg.StrOpt('logging_context_format_string',
               default='%(asctime)s %(levelname)s %(name)s [%(request_id)s '
                       '%(user_id)s %(project_id)s] %(instance)s'
                       '%(message)s',
               help='format string to use for log messages with context'),
    cfg.StrOpt('logging_default_format_string',
               default='%(asctime)s %(process)d %(levelname)s %(name)s [-]'
                       ' %(instance)s%(message)s',
               help='format string to use for log messages without context'),
    cfg.StrOpt('logging_debug_format_suffix',
               default='%(funcName)s %(pathname)s:%(lineno)d',
               help='data to append to log format when level is DEBUG'),

with these settings, it is difficult for other components to use it.

[yong sheng gong (gongysh)]

Not all of RPC calling has the [%(request_id)s '
                       '%(user_id)s %(project_id)s] %(instance)s'

[yong sheng gong (gongysh)]

Can handler have two formaters at the same time?
for handler in log_root.handlers:
        datefmt = CONF.log_date_format
        if CONF.log_format:
            handler.setFormatter(logging.Formatter(fmt=CONF.log_format,
                                                   datefmt=datefmt))
        handler.setFormatter(LegacyFormatter(datefmt=datefmt))