This reverts the effect of MDEV-21654 and includes
pam_mariadb_mtr in the mariadb-test-data Deb package.
This allows our CI systems to run tests on the
pam implementation on Debian systems.
As the pam configuration can include a full path,
we've change the installation of the pam module
pam_mariadb_mtr.so to under the /usr/lib*/plugins/test_pam_modules
directory and configured the pam configuration file,
suite/plugins/pam/mariadb_mtr, to include the
full path to pam_mariadb_mtr.so.
7efbb0d0b2