Should verify that:
- Compound hashed indexes cannot be built while in FCV 4.2.
- Can be built and queried in FCV 4.4
- Compound hashed Indexes created under FCV 4.4 can be used when FCV is downgraded to 4.2, but no further indexes can be built.
- Downgrading to binary 4.2 while a compound hashed index exists will cause an fassert, but the mongod can be started successfully if the index is dropped before downgrade.