vfs: don't treat fl_type as a bitmap

vfs: don't treat fl_type as a bitmap

The rules for fl_type are rather convoluted. Typically it's treated as
holding specific values, except in the case of LOCK_MAND, in which case
it can be or'ed with LOCK_READ|LOCK_WRITE.

On some arches F_WRLCK == 2 and F_UNLCK == 3, so and'ing with F_WRLCK will also
catch the F_UNLCK case. It's unlikely in either case here that we'd ever see
F_UNLCK since those shouldn't end up on any lists, but it's still best to be
consistent.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>