When wsrep_on is disabled all Galera features and checks should be also.

MariaDB [(none)]> show variables like 'wsrep%' ;

+---------------------------------+-----------------------------------------+

| Variable_name | Value |

+---------------------------------+-----------------------------------------+

| wsrep_osu_method | TOI |

| wsrep_auto_increment_control | ON |

| wsrep_causal_reads | OFF |

| wsrep_certify_nonpk | ON |

| wsrep_cluster_address | |

| wsrep_cluster_name | my_wsrep_cluster |

| wsrep_convert_lock_to_trx | OFF |

| wsrep_data_home_dir | /opt/hd/db/mysql/data1/ |

| wsrep_dbug_option | |

| wsrep_debug | OFF |

| wsrep_desync | OFF |

| wsrep_dirty_reads | OFF |

| wsrep_drupal_282555_workaround | OFF |

| wsrep_forced_binlog_format | NONE |

| wsrep_gtid_domain_id | 0 |

| wsrep_gtid_mode | OFF |

| wsrep_load_data_splitting | ON |

| wsrep_log_conflicts | OFF |

| wsrep_max_ws_rows | 0 |

| wsrep_max_ws_size | 2147483647 |

| wsrep_mysql_replication_bundle | 0 |

| wsrep_node_address | |

| wsrep_node_incoming_address | AUTO |

| wsrep_node_name | ln3e49.homedepot.com |

| wsrep_notify_cmd | |

| wsrep_on | OFF |

| wsrep_patch_version | wsrep_25.19 |

| wsrep_provider | none |

| wsrep_provider_options | |

| wsrep_recover | OFF |

| wsrep_replicate_myisam | OFF |

| wsrep_restart_slave | OFF |

| wsrep_retry_autocommit | 1 |

| wsrep_slave_fk_checks | ON |

| wsrep_slave_uk_checks | OFF |

| wsrep_slave_threads | 1 |

| wsrep_sst_auth | |

| wsrep_sst_donor | |

| wsrep_sst_donor_rejects_queries | OFF |

| wsrep_sst_method | rsync |

| wsrep_sst_receive_address | AUTO |

| wsrep_start_position | 00000000-0000-0000-0000-000000000000:-1 |

| wsrep_sync_wait | 0 |

+---------------------------------+-----------------------------------------+

2017-10-02 14:52:49 140269844322048 [ERROR] InnoDB: WSREP: referenced FK check fail: 15 index user_class_ibfk_1 table XXXXXXXXXXXXXXX