Fix test when home controls hsum flag enabled

The HomeControlsDreamStartableTest currently fails when the home
controls hsum flag is enabled. This change parameterizes the test to
ensure we have coverage with both the flag on and off. It also makes
some other cleanup updates to the test.

Flag: EXEMPT test fix
Bug: 370691405
Test: atest HomeControlsDreamStartableTest
Change-Id: Ied928df0451f2fac0131e050b5fff668c93fee87