Merge pull request #25229 from bboreham/multi-unix-sockets

Fix Upstart post-start script when using multiple Unix sockets

contrib/init/upstart/docker.conf

@@ -58,7 +58,7 @@ post-start script
 	if ! printf "%s" "$DOCKER_OPTS" | grep -qE -e '-H|--host'; then
 		DOCKER_SOCKET=/var/run/docker.sock
 	else
-		DOCKER_SOCKET=$(printf "%s" "$DOCKER_OPTS" | grep -oP -e '(-H|--host)\W*unix://\K(\S+)')
+		DOCKER_SOCKET=$(printf "%s" "$DOCKER_OPTS" | grep -oP -e '(-H|--host)\W*unix://\K(\S+)' | sed 1q)
 	fi
 
 	if [ -n "$DOCKER_SOCKET" ]; then