RunOn.. commands - Propagate errors in restart configurations (#2828)

* RunOnX commands - Propagate errors in restart configurations

* apply gofmt

---------

Co-authored-by: James Bohnert <jbohnert@haivision.com>
Co-authored-by: aler9 <46489434+aler9@users.noreply.github.com>

internal/externalcmd/cmd.go

@@ -87,7 +87,11 @@ func (e *Cmd) run() {
 			return
 		}
 
-		e.onExit(fmt.Errorf("command exited with code 0"))
+		if err != nil {
+			e.onExit(err)
+		} else {
+			e.onExit(fmt.Errorf("command exited with code 0"))
+		}
 
 		select {
 		case <-time.After(restartPause):