ldb: repack old format database if GUID indexing enabled

ldb: repack old format database if GUID indexing enabled

VERY IMPORTANT PATCH
Now that we have a new packing format, we need to enable it by repacking
the database. We've decided to link all new database features together,
so once GUID indexing is enabled, the database will be repacked with
version 2 format. Repacking is done following the same iterate pattern as
reindexing.

Signed-off-by: Aaron Haslett <aaronhaslett@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>