Ignore SIGPIPE events, resolves #19728

Using golang 1.6, is it now possible to ignore SIGPIPE events on
stdout/stderr.  Previous versions of the golang library cached 10
events and then killed the process receiving the events.

systemd-journald sends SIGPIPE events when jounald is restarted and
the target of the unit file writes to stdout/stderr. Docker logs to stdout/stderr.

This patch silently ignores all SIGPIPE events.

Signed-off-by: Jhon Honce <jhonce@redhat.com>

cmd/dockerd/daemon.go

@@ -127,6 +127,11 @@ func (cli *DaemonCli) start() (err error) {
 	stopc := make(chan bool)
 	defer close(stopc)
 
+	signal.Trap(func() {
+		cli.stop()
+		<-stopc // wait for daemonCli.start() to return
+	})
+
 	// warn from uuid package when running the daemon
 	uuid.Loggerf = logrus.Warnf
 
@@ -280,11 +285,6 @@ func (cli *DaemonCli) start() (err error) {
 	serveAPIWait := make(chan error)
 	go api.Wait(serveAPIWait)
 
-	signal.Trap(func() {
-		cli.stop()
-		<-stopc // wait for daemonCli.start() to return
-	})
-
 	// after the daemon is done setting up we can notify systemd api
 	notifySystem()