locksrv/lock: Improve error message for soft release when lock not held
locksrv/lock: Improve error message for soft release when lock not held

- Produce a more informative error message than "unable to open nonce file"
when we're asked for a soft release but the lock is not currently held

- Cleanups in release path

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr