Merge pull request #473 from docker/fix_warn_forward_signal

Do not display warning if cannot forward signal to child.

cli/mobycli/exec.go

@@ -72,10 +72,8 @@ func Exec() {
 				if cmd.Process == nil {
 					continue // can happen if receiving signal before the process is actually started
 				}
-				err := cmd.Process.Signal(sig)
-				if err != nil {
-					fmt.Printf("WARNING could not forward signal %s to %s : %s\n", sig.String(), ComDockerCli, err.Error())
-				}
+				// nolint errcheck
+				cmd.Process.Signal(sig)
 			case <-childExit:
 				return
 			}