run-tests: don't mask errors when a server fails to start
There are sporadic instances of this on Windows. They seem to happen more
frequently after the test machine is rebooted, although the only way to hit it
on my laptop is to loop certain tests with -j9 for hours. The problem with
masking out the specific failure is that there's no way to know if it's the same
line in the test that's failing, or if it is random.
The justification for adding this masking in 52e9e63f1495 was that the failures
occur regularly, but that's not the case anymore. The port number is still
printed, in case that turns out to be useful.
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).