MariaDB restart slave mariadb handler is called in genconfig action

When use genconfig action of Kolla-ansible handler "mariadb : restart slave mariadb" is invoked and failed due to master_host is defined in mariadb bootstrap task.

RUNNING HANDLER [mariadb : restart slave mariadb] ********************************************
fatal: [node2]: FAILED! => {"failed": true, "msg": "The conditional check 'inventory_hostname != master_host' failed. The error was: error while evaluating conditional (inventory_hostname != master_host): 'master_host' is undefined\n\nThe error appears to have been in '/data/openstack/pike/kolla-ansible/ansible/roles/mariadb/handlers/main.yml': line 44, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: restart slave mariadb\n ^ here\n"}
fatal: [node1]: FAILED! => {"failed": true, "msg": "The conditional check 'inventory_hostname != master_host' failed. The error was: error while evaluating conditional (inventory_hostname != master_host): 'master_host' is undefined\n\nThe error appears to have been in '/data/openstack/pike/kolla-ansible/ansible/roles/mariadb/handlers/main.yml': line 44, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: restart slave mariadb\n ^ here\n"}
fatal: [node3]: FAILED! => {"failed": true, "msg": "The conditional check 'inventory_hostname != master_host' failed. The error was: error while evaluating conditional (inventory_hostname != master_host): 'master_host' is undefined\n\nThe error appears to have been in '/data/openstack/pike/kolla-ansible/ansible/roles/mariadb/handlers/main.yml': line 44, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: restart slave mariadb\n ^ here\n"}