s4/dsdb/tests/python: Restore embed NULL tests for Python3

s4/dsdb/tests/python: Restore embed NULL tests for Python3

commit: 34ca15fb042e42773854c093ad9f1e67696c90ac changed the
test so embedded NULLs were avoided when python3 was used.
This was due to the fact the string comparison function
'locale.strcoll' cannot handle embedded NULLs. This commit

a) Restores the test data using embedded NULLs which was
   not used depending on the python runtime version
b) Removes the problematic calculation of expected sorting order
   and instead uses sort order data stored in files.

Signed-off-by: Noel Power <noel.power@suse.com>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>