Merge pull request #19588 from tianon/docker.default-systemd

Add a note to /etc/default/docker noting that it does not apply to systemd
Upstream-commit: 05b2f342fd73d1624fac3d3107700d05caa0ac18
Component: engine

components/engine/contrib/init/sysvinit-debian/docker.default

@@ -1,5 +1,12 @@
 # Docker Upstart and SysVinit configuration file
 
+#
+# THIS FILE DOES NOT APPLY TO SYSTEMD
+#
+#   Please see the documentation for "systemd drop-ins":
+#   https://docs.docker.com/engine/articles/systemd/
+#
+
 # Customize location of Docker binary (especially for development testing).
 #DOCKER="/usr/local/bin/docker"