Fixes for nested class groups

Removing nested class groups overlooked a couple of instances of nested
class groups, and moved some classes to class_group sections of
$scenario.yaml files. Replace remaining nested groups with their
constituent class groups and classes, and move classes from class_groups
to classes stanzas of $scenario.yaml files.

Change-Id: I4cc11c2711892db4a505136f4f6ea868c8555079
Partial-Bug: #1303973
Merge "Fixes for nested class groups"