Client: Test (C++)
Patch: John Sirois
Instead of using a fixed port, use an ephemeral port to improve
robustness and make way for parallelizability.
This change has an undesirable amount of repeated code but this fact is
not different from the prior so being a bit expedient here. Ideally
setup of a `TServerSocket` listening on an ephemeral port would be DRYed
up into a helper of some sort.
This closes#857