[PATCH] fuse: fail file operations on bad inode

Make file operations on a bad inode fail.  This just makes things a
bit more consistent.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>