We want to be able to have topologies of older version (for example 0.10) to run on 2.x cluster. User might submit topologies with 0.10 configs which includes "backtype.storm". It will fail the validation process on the nimbus because the "backtype.storm.XXX" class not found. For now it's really just about TOPOLOGY_SCHEDULER_STRATEGY config. We might want to loosen the constraints for @isImplementationOfClass so that if "backtype.storm.XXX" is not found, we try with "org.apache.storm.XXX and if it passed, we let it pass the validation.