tools: open `test.tap` file in write-binary mode

By default the logfile is opened in append mode. This commit makes sure
that the file is opened in write-binary mode, so that the file will be
created if it doesn't exist or overwrite if it exists.

Fixes: #2834

PR-URL: #2837
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Alexis Campailla <orangemocha@nodejs.org>

tools/test.py

@@ -1418,7 +1418,7 @@ def Main():
   logger.addHandler(ch)
   logger.setLevel(logging.INFO)
   if options.logfile:
-    fh = logging.FileHandler(options.logfile)
+    fh = logging.FileHandler(options.logfile, mode='wb')
     logger.addHandler(fh)
 
   workspace = abspath(join(dirname(sys.argv[0]), '..'))