Backport 'ident' from python 3.3 for Oslo's SysLogHandler

To honour RFC5424 requirements add use_syslog_rfc_format
config option (False) to add APP-NAME to syslog message
before MSG part to reflect application or service name.

To include APP-NAME field in the logs if using log_config_append
make sure you've configured handler's class as:
[handler_foo]
class = openstack.common.log.RFCSysLogHandler

Closes-bug: #904307

Change-Id: I3815e6dc47e206e15f9da90ebbba5ca00c3ae641
Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>