Only add logging handlers if there currently aren't any

This corrects an odd problem where Horizon would stand up multiple
client objects, which would cause duplicate/triplicate/dozens of
repeated log lines in its log files, due to multiple identical
handlers being added to the logging object

Fixes Bug 1182678

Change-Id: I020b3999c9008b996286ccb74a7801c96c43e71c

keystoneclient/client.py

@@ -113,7 +113,7 @@ class HTTPClient(object):
 
         # logging setup
         self.debug_log = debug
-        if self.debug_log:
+        if self.debug_log and not _logger.handlers:
             ch = logging.StreamHandler()
             _logger.setLevel(logging.DEBUG)
             _logger.addHandler(ch)