handle errors during debugserver startup and add helper function

[Ukalnins]

Sometimes, when device is restarted and ios-deploy mounts the new image, user may get "invalid service" error due to race condition while ios is scanning the image.

While debugging this error, I also received "cannot send message" error in the same place, so I added handling for both errors.

As the same pattern is repeated a lot of times, added helper function.

[gabebear]

OOoof... you seem to be correct.

I'd like to play with this a bit; I will look at this sometime today. It hits a lot of code that as far as I know uses a lot of guesswork on what Apple is doing.

[Ukalnins]

For the race condition for mount I mostly followed the "Console" output and just made an assumption that the "ImageMounted" event within iOS is processed asynchronously from MountImage call, so it just made sense.

[ivanhernandez13]

I'm unable to repro the original issue, the change itself looks fine to me. It's essentially trying once more on error.

I wish there was a way around using sleep and instead listening for the actual event but I'm not aware of a way to do that.

[Ukalnins]

I haven't been able to reliably repeat it on any 64bit device. I was seeing this problem on our 32bit device pool that needs constant reboots due to other problems, so I tested on 5C with idevicediagnostics -u .. restart && sleep 45 && ios-deploy -b .. -i ... --noninteract -m -d that failed in around 1 in 4 times. One day it was invalid service, the other - cannot send message, so it's probably also related to moon-phases or something.