BUG-1410 Fix config yang generator parsing dependency containers

Check if the grouping used is of type service-ref.
Until now, any container containing grouping was considered a dependency.
Add test for this case.

Change-Id: I9299b2b39e393d940c71a41f8d33d737564f2530
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>
Merge "BUG-1410 Fix config yang generator parsing dependency containers"