Draft: Don't fetch votes in parallel

Hi, this is a WIP MR. I currently don't know a good way to test this actually works: I could mock connection_get_by_type_addr_port_purpose and directory_initiate_request, but that's not really a test because I am basically hoping that those two functions work together the way I hope they do. But there doesn't really seem to be a smart way to disable actually making a connection but still having the fake connection recorded and able to look up. My current best plan is to test it on the live network using a lot of additional log statements, and writing the test using mocking as best I can, unless a better idea emerges?