netcmd/ldapcmp: rename __eq__ to diff

This method actually changed both objects and print info.
__eq__ is not a proper name and is not designed for this case.
Rename to diff.

Signed-off-by: Joe Guo <joeg@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
