logger.PutMessage, added in #28762 (v17.04.0-ce), clears msg.Source. So journald
and syslog were treating stderr messages as if they were stdout.
Signed-off-by: David Glasser <glasser@davidglasser.net>
Upstream-commit: 917050c5728f2fb9958ccb3ab66a23766f741adc
Component: engine