fix unit test now that coverage files are in a dir#29

sksamuel merged 1 commit intoscoverage:masterscoverage/scalac-scoverage-plugin:masterfrom

RichardBradley:issue-19-windows-race-condition-file-per-threadRichardBradley/scalac-scoverage-plugin:issue-19-windows-race-condition-file-per-threadCopy head branch name to clipboard