selftest: Tweak PSO test-suite name

selftest: Tweak PSO test-suite name

There are 2 different PSO tests:
- make test TESTS=ldap.password_settings
- make test TESTS=samba_tool.passwordsettings

There's also another test that's completely unrelated to PSOs:
- make test TESTS=blackbox.password_settings

This patch renames ldap.password_settings --> ldap.passwordsettings.
This means 'make test TESTS=passwordsettings' will run both PSO tests,
but not the unrelated blackbox test.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Sep 21 22:58:17 CEST 2018 on sn-devel-144