tests: use proxy str directly (imrpove test cov)

Author: ikreymer

tests/server_thread.py

@@ -22,6 +22,7 @@ def __init__(self, make_httpd, config_file=None):
         self.port = self.httpd.socket.getsockname()[1]
 
         proxy_str = 'http://localhost:' + str(self.port)
+        self.proxy_str = proxy_str
         self.proxy_dict = {'http': proxy_str,
                            'https': proxy_str}