Cross test log file cannot be browsed when served in HTTP server

Links to log files in cross test result.html does not work when served in HTTP server.
It is especially crucial for Chrome because alternative way (use of file:// scheme) does not work on it.

Steps to reproduce:

1. Run any number of cross test if never run once on your environment
2. As test output suggests, run HTTP server on the test directory, like cd test && python -m SimpleHTTPServer 8001 for python2
3. Browse http://localhost:8001/result.html using a browser
4. Click on any server or client link in Result(log) column

Expected result:

The log file content is displayed or at least a download dialog pops up.

Actual result:

404 Not found.

Cause:

Link path format in results.json file should be relative rather than absolute file paths.