Handles child failure on session validate

This change ensures that we fail to validate for all children and the
parent when a single child fails to validate. Without this change, we
were leaving orphaned parent sessions when a child failed and could
theoretically leave it referencing other children with a single invalid
child session ID. Instead, we now fail all related sessions when the
parent or child fail to validate.

Test: atest AtomicInstallTests
Fixes: 144567152
Change-Id: I735a41473237432efa981d25641c8a343fdac71f