Sync log.py from oslo
Sync log.py from oslo

Add use_syslog_rfc_format config option. Default value is False.
If enabled, will add APP-NAME before the MSG part of the syslog message.

Fixes bug: #904307

Change-Id: Idd664bc98532e3a557dde5cbee213ca597d4e2e5

JioCloud/glance,stevelle/glance,jumpstarter-io/glance,saeki-masaki/glance,redhat-openstack/glance,kfwang/Glance-OVA-OVF,openstack/glance,stevelle/glance,JioCloud/glance,paramite/glance,akash1808/glance,ozamiatin/glance,paramite/glance,rajalokan/glance,takeshineshiro/glance,dims/glance,ozamiatin/glance,akash1808/glance,kfwang/Glance-OVA-OVF,tanglei528/glance,darren-wang/gl,redhat-openstack/glance,wkoathp/glance,klmitch/glance,openstack/glance,saeki-masaki/glance,tanglei528/glance,jumpstarter-io/glance,scripnichenko/glance,scripnichenko/glance,sigmavirus24/glance,sigmavirus24/glance,rajalokan/glance,wkoathp/glance,vuntz/glance,dims/glance,takeshineshiro/glance,klmitch/glance,vuntz/glance,openstack/glance,darren-wang/gl