Format record before passing it to syslog
Format record before passing it to syslog

That solves two problems:
 * formatting specifed in options logging_context_format_string and
   logging_default_format_string is not applied to log entries
 * exception stack traces are not sent over syslog

Change-Id: I1154c521014bedb4f88c094007fb612e71dace65
Closes-Bug: #1526743
Closes-Bug: #1514828

openstack/oslo.log