Add system time to /info

This change adds daemon's system time as RFC3339Nano to the `/info` endpoint
and shows in a more readable format (UnixDate) in `docker -D info` output.

I will be using this to fix the clock skew between the remote test host and
the CI machines running `docker events`-related tests as they're using `--since`
and `--until` and the timestamps are not matching when daemon is not on the
same machine.

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>
Upstream-commit: 2977fd2b7aed42008ca2ad90dcd8fec5ead4e86b
Component: engine

components/engine/api/client/commands.go

@@ -578,6 +578,14 @@ func (cli *DockerCli) CmdInfo(args ...string) error {
 		if remoteInfo.Exists("NGoroutines") {
 			fmt.Fprintf(cli.out, "Goroutines: %d\n", remoteInfo.GetInt("NGoroutines"))
 		}
+		if remoteInfo.Exists("SystemTime") {
+			t, err := remoteInfo.GetTime("SystemTime")
+			if err != nil {
+				log.Errorf("Error reading system time: %v", err)
+			} else {
+				fmt.Fprintf(cli.out, "System Time: %s\n", t.Format(time.UnixDate))
+			}
+		}
 		if remoteInfo.Exists("NEventsListener") {
 			fmt.Fprintf(cli.out, "EventsListeners: %d\n", remoteInfo.GetInt("NEventsListener"))
 		}