fuse: Fix bug in `open`
fuse: Fix bug in `open`

When a file record for the corresponding file is not found, pass the
call through to the underlying filesystem.

Signed-off-by: Ramkumar Ramachandra <5c355d1d38066ed0c5de420d67c1b5ed0687c4bd@gmail.com>

artagnon/phoenixfs,artagnon/phoenixfs,artagnon/phoenixfs