fusefs: fix two bugs regarding fcntl file locks
- F_SETLKW (blocking) operations would be sent to the FUSE server as F_SETLK (non-blocking).
- Release operations, F_SETLK with lk_type = F_UNLCK, would simply return EINVAL.
PR: 253500
Reported by: John Millikin <jmillikin@gmail.com>
MFC after: 2 weeks