Run GetVersion in a goroutine

[babolivier]

When fetching the server version, if the endpoint times out, it means that we have to wait an extra 30s before getting our results, meaning that if everything times out we have to wait for 40s. Doing so is not necessary for tests, thus the request can be run in parallel with the connection reports, and save 10s.

Bonus points if we standardise the timeout by creating the gomatrixserverlib client using NewClientWithTimeout instead of NewClient so that it takes up to as much time as other requests.