Refactoring killing servers.

Made it less chatty, and use a for loop rather than a while loop (so
bugs are less likely to cause infinite loops).
Removing more print statements so it's easier to see what's going on.
Further print statement removal.

Using logging would be better, but in this case I think these print
statements don't add anything.
Reducing test verbosity (quiet should be the default, we already get
full tracebacks on failing tests).
Use standard Python tracebacks.
Merge pull request #34 from ahlmss/less_verbose_testing

Less verbose testing