Change maas_notification_plan to npManaged

When set to npTechnicalContactEmail for customers without a cloud
account, alarm creation will fail with an "Unable to create Alarm due to issues with account contact information. Please contact support"
error. Changing to npManaged allows alert creation to complete so alarm
tickets can be created.

Issue rcbops/ansible-lxc-rpc#402
Merge pull request #407 from claco/issues/402

Change maas_notification_plan to npManaged