Try to reach the cozy-controller as soon as possible

Sleeping for a fixed amount of time seems too restrictive to me. Either, I propose to run the curl command to access the cozy controller, ignore if it fails, wait for one second, until the script can reach the end point. We timeout after 60 attempts = 60 seconds, which is slightly more that the previous 20 seconds constant, but in my case it was needed as my rPI was already busy.

Bonus points: we can delete the is_arm function which is not necessary anymore.