Put finalized child staged session at correct place in dumpsys

Child staged sessions do not get marked as applied or failed
individually. We only mark the parent session as such. As such, child
staged sessions were being printed as active sessions in dumpsys.

Bug: 162518337
Test: used `adb install-multi-package` to create multi package session
      and manually checked dumpsys that child session gets printed
      under correct section.
Change-Id: I88d41085a49bba6b29502a501af2fa5ab1a9dbae