BUG-862: Fixed resolving of NotificationDefinition.

  - Deduplicated same code in TransformerGenerator

Change-Id: I1a422aa18d43b86a3132884e539cd65b90a64dfe
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
(cherry picked from commit 98740ce4b370937d51f204cbe4226d0638f8ea3e)
Merge "BUG-862: Fixed resolving of NotificationDefinition." into stable/hydrogen