smbd: Simplify share_mode_lock.c

smbd: Simplify share_mode_lock.c

Do explicit refcounting instead of talloc_reference(). A later patch
will introduce a share_mode_do_locked() routine that can be nested
arbitrarily with get_share_mode_lock(). To do sanity checks for proper
nesting, share_mode_do_locked needs to be aware of the reference
counts for "static_share_mode_lock".

Why is share_mode_memcache_delete() gone? In parse_share_modes() we
already move the data out of the cache, share_mode_lock_destructor()
we don't even bother re-adding the share_mode_data to the cache if
it does not have share entries, because the next opener will invent a
new seqnum anyway.

Also: Less talloc_reference(), less lines of code.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>