'scw run' and 'scw exec -w' should exit if server state changed to 'stopped'

[moul]

Sometimes, the server won't boot up from start to finish, i.e: if there are no spot left for this kind of instance, scw run and scw exec -w are polling the API to get the current state, the expected behavior is an exit 1 as soon as the server state is 'stopped' from the API point of view