Add Unit test cases for OomAdjuster.updateOomAdj

Bug: 138673927
Test: atest MockingOomAdjusterTests
      cts-tradefed run singleCommand cts-dev -m CtsAppTestCases \
      -t android.app.cts.ActivityManagerProcessStateTest

Change-Id: Iea034107d65835b9312df3eb9f29d6afc7266910
1 file changed