Add the ability to override the service request message.

https://bugzilla.redhat.com/show_bug.cgi?id=1161253

Allow automate method to override the default request status message
displayed as "last message".
Added automate service model user_message helper methods.
Changed service_template_provision_task after_ae_delivery method for
reload and user_message override.
Added tests.
Merge pull request #1051 from tinaafitz/user_message_changes

Enable Service Provisioning request message override.