Remove WM lock from simple conditions in oom-adj update

Though the conditions might get an intermediate state, the
original code with lock also has the similar symptom because
oom-adj calculation doesn't lock WM in entire update procedure.

And if there are important state changes, WM should schedule an
oom-adj update after the oom related field in WM are computed.
So it should eventually calculate the score steadily.

Bug: 159104503
Test: MockingOomAdjusterTests
      ActivityTaskManagerServiceTests
Change-Id: I75b715607203785f4fc6c0a2a18ed0a84d0a246a