Clean code in cmstestsuite

Move definition of check functions outside the start_* functions. Also,
for web servers, check that both the RPC and the HTTP servers are up.
Fix tests

This code was failing since we moved ScoringService among the
contest-agnostic services. On the other hand, ProxyService needs to be
restarted.
Avoid an infinite loop which could jam ProxyService

If an operation with an empty dictionary of entities to create/update
was added to the queue, data[i] could become empty with task_count[i]
still being positive. Therefore no data would have ever been sent (and
thus task_count would have never been reset to zero) but the loop would
also have never yielded to other greenlets, making ProxyService stuck
(and taking up 100% of the CPU).
Remove useless code from ProxyService

We used a joinable queue and we had an additional second structure to
keep track of how many task we had done. Since they were not necessary,
this commit removes them altogether.
Small fix to RWS