MDEV-39413 wsrep unsafe handling of parameters

When server is started with unsafe parameter --exec could
return also error 134. Furthermore, --exed pkill could
return error 15. Added these error codes as accepted.

Author: janlindstrom

mysql-test/suite/galera/t/galera_sst_mariabackup_encrypt_with_key_server.test

@@ -45,7 +45,7 @@ call mtr.add_suppression('Removing .*/xtrabackup_galera_info file due to signal'
 --exec echo ssl-key=$MYSQL_TEST_DIR/std_data/server-new-key.pem >> $MYSQLTEST_VARDIR/my.cnf
 
 --echo # start the server
---error 0
+--error 0,134
 --exec $MYSQLD_LAST_CMD
 --echo # the server failed to start
 
@@ -55,6 +55,7 @@ call mtr.add_suppression('Removing .*/xtrabackup_galera_info file due to signal'
 --echo # cleanup
 # we have to kill joiner's socat here, because the donor has aborted SST
 # and joiner's socat will timeout in 5 minutes
+--error 0,15
 --exec pkill -f 'socat.*server-new-cert'
 --exec echo ssl-cert=$MYSQL_TEST_DIR/std_data/server-cert.pem >> $MYSQLTEST_VARDIR/my.cnf
 --exec echo ssl-key=$MYSQL_TEST_DIR/std_data/server-key.pem >> $MYSQLTEST_VARDIR/my.cnf