Interpret transferred integers as signed again

This fixes an issue with unsigned values ending up in signed fields and
missing sign extension.

See:
https://bugs.debian.org/739330
Fix nslcd-test.conf permissions for test

This ensures that configuration file is not world readable when the
tests are run. This avoids test failure for the use of the rootpwmodpw
option.
Run the correct executables for the tests

This fixes issues with running the tests when using a separate build
directory (fixes ef0eddaa).