Currently we don't have any suites that test FCBIS when the syncing node's sync source is killed or a network error occurs.

We have:

• replica_sets_fcbis_jscore_passthrough
• concurrency_sharded_initial_sync
• various config_fuzzer suites that can use FCBIS

But none of these cause network / sync source problems while FCBIS is running.

Note that this ticket is just highlighting the lack of coverage - this isn't a recommendation to add a new passthrough suite. Any solution that adds coverage is acceptable.

See comments for more info.