Clean up pick_random_server() and filter_protocol() and their

call sites.

Remove unused imports and redundant random pick of server

gui/qt/network_dialog.py

@@ -23,7 +23,7 @@ import os.path, json, ast, traceback
 
 from PyQt4.QtGui import *
 from PyQt4.QtCore import *
-from electrum import DEFAULT_SERVERS, DEFAULT_PORTS
+from electrum import DEFAULT_PORTS
 
 from util import *