The net ansible Mechanism driver fails to apply vlan configuration to a port if it already has any config. 

Errors from the neutron api log (which ironic nodes are being clean for the first time)
2018-10-23 08:57:30.904 30 ERROR neutron.plugins.ml2.managers [req-235ea2ba-0f8a-426f-a605-74c70b3a4608 cedcec64f5b24025848a2130a5892191 a2d65540a46944af95b64d72065400be - default default] Mechanism driver ansible failed in bind_port: AnsibleRunnerException: ^M


2018-10-23 08:57:17.723 30 ERROR neutron.plugins.ml2.managers  fatal: [switch1]: FAILED! => {"changed": false, "msg": "error editing configuration: <?xml version=\"1.0\" encoding=\"UTF-8\"?><rpc-reply xmlns=\"urn:ietf:params:xml:ns:netconf:base:1.0\" xmlns:junos=\"http://xml.juniper.net/junos/17.3R2/junos\" xmlns:nc=\"urn:ietf:params:xml:ns:netconf:base:1.0\" message-id=\"urn:uuid:a333b53e-d6a1-11e8-91cf-588a5a535fd9\">\n<commit-results>\n<rpc-error>\n<error-type>protocol</error-type>\n<error-tag>operation-failed</error-tag>\n<error-severity>error</error-severity>\n<source-daemon>\nl2ald\n</source-daemon>\n<error-path>\n[edit interfaces xe-0/0/6 unit 0 family ethernet-switching vlan]\n</error-path>\n<error-info>\n<bad-element>\nmembers 1201-1202\n</bad-element>\n</error-info>\n<error-message>\nVlan range format not supported if interface-mode is access\n</error-message>\n</rpc-error>\n<rpc-error>\n<error-type>protocol</error-type>\n<error-tag>operation-failed</error-tag>\n<error-severity>error</error-severity>\n<error-message>\nconfiguration check-out failed\n</error-message>\n</rpc-error>\n</commit-results>\n</rpc-reply>"}


Should this happen, deleting the config from the switch for the ports allows the process to continue, once this is done once, net ansible cleans up port config as it goes so it doesn't need to be manually done a second time.