This modifies the goclean.sh script to run tests with the
race detector enabled. It also enables code coverage, and
uploads the results to coveralls.io.
Running tests with -race and -cover flags was disabled in
6487ba1 and 6788df7 respectively, due to some limits on
time/goroutines being hit on Travis CI. Since we have
migrated to GitHub Actions, it is desirable to bring them
back.