Update haproxy-statsd to python3

Change-Id: I1b5c15f0c47a4bf1261abaf6d4e336aad5339c5b

docker/haproxy-statsd/haproxy-statsd.py

@@ -120,11 +120,11 @@ class HAProxy(object):
 
     def command(self, command):
         with self.socket as socket:
-            socket.send(command + '\n')
+            socket.send((command + '\n').encode('utf8'))
             data = ''
             while True:
                 r = socket.recv(4096)
-                data += r
+                data += r.decode('utf8')
                 if not r:
                     break
             return data