The test setFCV_collmod_transaction_rollback interrupts the unique index upgrade collmod in 4.2. It tests that the collmod transaction successfully rolls back after the interrupt. Post 4.2 the same upgrade collMod will not be available, hence this test could be removed. 

The testscript also contains a similar test for the index ttl update collMod which should be retained. The testscript can then be moved to a directory outside of multiversion directory.