Changed tests to run inside transactions when needed
Safeguard against NullPointerException in ConstraintVerificationFKE

o Use evidence() instead of evidence when looping in getUserMessage()
Fix LuceneIndexRecoveryIT.shouldNotAddTwiceDuringRecoveryIfCrashedDuringPopulation

o Test was not deterministic about completion of population job
o Cleaned up/reverted changes in FlippableIndexProxy made because of the above issue
o Made ControlledPopulationSchemaIndexProvider optionally take a delegate