Fix telemetry_unittests.py on Windows by adding sys.executable to args

BUG=422235
R=sergiyb@chromium.org

Review URL: https://codereview.chromium.org/677023002

Cr-Commit-Position: refs/heads/master@{#301081}

testing/scripts/telemetry_unittests.py

@@ -21,6 +21,7 @@ def main_run(args):
         sys.executable,
         os.path.join(args.paths['build'], 'scripts', 'tools', 'runit.py'),
         '--show-path',
+        sys.executable,
         os.path.join(args.paths['build'], 'scripts', 'slave', 'runtest.py'),
         '--target', args.build_config_fs,
         '--xvfb',