each container in run_change_password_test mounts its own volume

selinux does not allow two containers accesing one mounting directory if
mounted with Z option

Author: zmiklank

test/run_test

@@ -634,6 +634,11 @@ $volume_options
 
   echo "  Changing passwords"
 
+  # create separate mounting directory for second container, as selinux does
+  # not allow two containers accesing one mounting directory if mounted with
+  # Z option
+  create_volume_dir || ret=1
+
   DOCKER_ARGS="
 -e POSTGRESQL_DATABASE=${database}
 -e POSTGRESQL_USER=${user}