A series of synchronization fixes:

A series of synchronization fixes:
 - remote_kill can be told not to wait, for increase parallelism if you'll be waiting later with remote_status
 - somehow TunProto.checkpid gets called before the PID is ready (maybe before the tun_connect script is spawned).
   In those cases, old pids get fetched, instead of simply retrying later.
   To solve this, TunProto._make_home removes old pidfiles
 - tests that didn't perform shutdown on exception conditions now do