run-tests: follow-up on the test-case format
It turns out the original regex doesn't support real test cases names like the
one Mercurial is using. Update the regex to being able to precisely select
them on the command line.
Differential Revision: https://phab.mercurial-scm.org/D3699
Run Mercurial tests with Vagrant:
$ vagrant up
$ vagrant ssh -c ./run-tests.sh