UTF8 decode portion of url for XML in http command_responder

so
GET http://domainÂ:Â HTTP/1.1

won't trigger Traceback

```
Traceback (most recent call last):
  File "/usr/lib64/python2.7/SocketServer.py", line 582, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/lib64/python2.7/SocketServer.py", line 323, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib64/python2.7/SocketServer.py", line 639, in __init__
    self.handle()
  File "/usr/lib64/python2.7/BaseHTTPServer.py", line 337, in handle
    self.handle_one_request()
  File "/usr/lib64/python2.7/BaseHTTPServer.py", line 325, in handle_one_request
    method()
  File "/usr/local/lib/python2.7/site-packages/Conpot-0.2.2-py2.7.egg/conpot/http/command_responder.py", line 593, in do_HEAD
    self.path.partition('?')[0] + '"]')
  File "lxml.etree.pyx", line 1833, in lxml.etree._ElementTree.xpath (src/lxml/lxml.etree.c:42103)
  File "xpath.pxi", line 326, in lxml.etree.XPathDocumentEvaluator.__call__ (src/lxml/lxml.etree.c:104333)
  File "apihelpers.pxi", line 1295, in lxml.etree._utf8 (src/lxml/lxml.etree.c:20212)
ValueError: All strings must be XML compatible: Unicode or ASCII, no NULL bytes
```