If the config server is unreachable, the migration will fail on the recipient shard here: https://github.com/mongodb/mongo/blob/d5140178b5eeeec4e8d1ab6d42072e0c0cba8a6a/src/mongo/db/s/migration_destination_manager.cpp#L846-L852

Consider moving the changelog writes to after setting DONE state. Make sure we don't break JS test expectations that look at op entries to wait for steps in the migration to occur, e.g. https://github.com/mongodb/mongo/blob/master/jstests/libs/chunk_manipulation_util.js#L125-L137