device/dmrun: add a clean up step that kills the app instance

When the dmrun tool successfully starts an app, it outputs a list
of steps the user has to perform to clean up the VM.
In case the dmrun tool was used in the ssh mode, the clean up
script didn't kill the app instance leaving it alive and active.

Change-Id: I78ad7d75ba22590551bb8e7a217f3174aaeef4e3
diff --git a/services/device/dmrun/dmrun.go b/services/device/dmrun/dmrun.go
index baff70d..e378295 100644
--- a/services/device/dmrun/dmrun.go
+++ b/services/device/dmrun/dmrun.go
@@ -119,7 +119,7 @@
 	workDir, err = ioutil.TempDir("", filepath.Base(os.Args[0]))
 	dieIfErr(err, "Couldn't set up work dir")
 	dieIfErr(os.Chmod(workDir, 0777), "Couldn't chmod work dir")
-	fmt.Println("Working dir: %s", workDir)
+	fmt.Printf("Working dir: %s\n", workDir)
 }
 
 // buildV23Binary builds the specified binary and returns the path to the
@@ -405,6 +405,7 @@
 	fmt.Printf("\t${JIRI_ROOT}/release/go/bin/debug logs read %s/logs/app.INFO\n", instanceName)
 
 	fmt.Println("Clean up the VM instance:")
+	fmt.Printf("\t${JIRI_ROOT}/release/go/bin/device kill %s\n", instanceName)
 	fmt.Printf("\t%s\n", vm.RunCommandForUser("sudo", "killall", "-9", "agentd", "deviced"))
 	fmt.Printf("\t%s\n", vm.DeleteCommandForUser())
 }