Deprecate use-syslog-rfc-format for removal

During J dev cycle the default logging format for syslog
was supposed to be changed to always provide APP-NAME for log messages.
It looks like the valid deprecation procedure was missed, so this
patch introduces it as appropriate:
* Deprecate for removal use-syslog-rfc-format since J dev cycle
  ended and we should follow the accepted decision.

DocImpact
Related-bug: #904307

Change-Id: Ic2e5bd127c9f3a0f2807a25f29d8693baf3d65f2
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

oslo_log/_options.py

@@ -65,8 +65,8 @@
     cfg.BoolOpt('use-syslog',
                 default=False,
                 help='Use syslog for logging. '
-                     'Existing syslog format is DEPRECATED during I, '
-                     'and changed in J to honor RFC5424.'),
+                     'Existing syslog format is DEPRECATED '
+                     'and will be changed later to honor RFC5424.'),
     cfg.BoolOpt('use-syslog-rfc-format',
                 default=True,
                 deprecated_for_removal=True,