Same as pr #2110 except for 4.2 branch
steps to test:
create a ring group with one extension and one user. This will add one user to v_ring_group_users table. Delete the ring group.
expected result:
ring group and all it's components are deleted
actual result
v_ring_group_user entry for this ring group is not deleted.
This fix: deletes v_ring_group_user when ring group is deleted.