fuse: reduce attributes invalidated on directory change

fuse: reduce attributes invalidated on directory change

When the contents of a directory is modified, some of its attributes may
also change, so they need to be invalidated.  But this isn't the case
for every attribute.  For instance, unlinking or creating a file doesn't
change the uid/gid of its parent directory.

This can cause unnecessary FUSE_GETATTRs to be sent to user-space.  For
example, fuse_permission() checks if mode, uid, and gid are valid and
will issue a FUSE_GETATTR if they're not, which results in an extra
FUSE_GETATTR request for every FUSE_UNLINK when removing files in the
same directory.

Signed-off-by: Konrad Sztyber <ksztyber@nvidia.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>