Run postUpdate on pending oom adjust updates for new OomAdjuster

Isolated process trimming happens as a part of the postUpdate step.
Service stops usual trigger a pending omm adjust update, so the isolated
process trim needs to happen on pending updates (which matches legacy
behavior)

Test: atest MockingOomAdjusterTests
Test: atest CtsStatsdAtomHostTestCases:AppExitHostTest
Fixes: 318574235
Change-Id: I4c29b852037526097d4b4994bc6575fe6925bb81