mlaunch: Improve output when failing to launch app on device because the device is locked

Sample output: https://gist.github.com/emaf/779fdf53f393fab0b522519396879c33

We might be able to do better than this.

Note that we have to poll in order to detect when a device is unlocked, which is unfortunate and causes the verbose log to be quite verbose.

@emaf is there any particular string the IDE/XVS is waiting for to detect this?

> "We are looking for output that starts with 'warning HE1031', but we can change that to anything else."