Update oslo log module

Changes -
 * Set stevedore log level to WARN by default
 * Add unicode coercion of logged messages to ContextFormatter
 * Correct coercion of logged message to unicode
 * Except socket.error if syslog isn't running
 * Fix E126 pep8 errors
 * Set keystonemiddleware and routes.middleware to log on WARN level
 * Adjust oslo logging to provide adapter is enabled for
 * Make logging_context_format_string optional in log.set_defaults
 * Add default log level for websocket

Change-Id: Ib0529a52c1b6f6328b1022c4a61da752258d01f9
Merge "Update oslo log module"