Merge changes I400fdd74,I18d70f22,Icc83aef3,I3a67dc87,I05b3e988

* changes:
  Make two classes _static_ inner classes, as recommended by FindBugs
  Suppress FindBugs null analysis warning in FlowDescriptorDtoTest
  Suppress FindBugs concurrency warning which is wrong
  Fix FindBugs null analysis problems due to wrong @Nullable
  Fix FindBugs level "Scariest" problem in SalAsyncConfigServiceImplTest