MDEV-15473 Isolate/sandbox PAM modules, so that they can't crash the server

tests fixed.

mysql-test/suite/plugins/suite.pm

@@ -12,9 +12,7 @@ sub cassandra_running() {
 
 sub skip_combinations {
   my %skip;
-  $skip{'t/pam.test'} = 'No pam setup for mtr'
-             unless -e '/etc/pam.d/mariadb_mtr';
-  $skip{'t/pam_v1.test'} = 'No pam setup for mtr'
+  $skip{'t/pam_init.inc'} = 'No pam setup for mtr'
              unless -e '/etc/pam.d/mariadb_mtr';
   $skip{'t/cassandra.test'} = 'Cassandra is not running'
              unless cassandra_running();

mysql-test/suite/plugins/t/pam_cleartext.test

-
+let $PAM_PLUGIN_VERSION= $AUTH_PAM_SO;
 --source pam_init.inc
 
 show variables like 'pam_use_%';