Feature compatibility version is no longer the same version that resharding started with, startingFCV: 9.0, currentFCV: upgrading from 9.0 to 9.1

is a known error added as part of SERVER-132223. It was added to close a race condition where resharding can start before FCV transition, and then commit before setFCV has a chance to abort it but after it has already transitioned the FCV. Which breaks a core assumption with resharding that it does not complete across an FCV transition. 

The move collection balancer policy (which is only used in tests) should allow for this error. Similar to how it already allows for ReshardCollectionInterruptedDueToFCVChange