tools: remove hyphen in TAP result

As it is, the TAP result shows an extra hyphen in front of test names.
Sample:
ci.nodejs.org/job/node-test-commit-osx/nodes=osx1010/454/tapResults/
This patch removes the extra hyphen.

PR-URL: https://github.com/nodejs/node/pull/2718


Reviewed-By: Johan Bergström <bugs@bergstroem.nu>