regedit: search values and repeat search from cursor positions

regedit: search values and repeat search from cursor positions

Recovering the search position from the cursors is safer than retaining
a pointer to the last node, as the pointer will become invalid if the
user deletes the item or refreshes the cache.

Signed-off-by: Chris Davis <cd.rattan@gmail.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>