fuse: fix attribute caching after create

Invalidate attributes on create, since st_ctime is updated.  Reported by
Szabolcs Szakacsits.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>