Fixing a file descriptor leak. Closes issue 22.

run_tests

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+PYTHONPATH=. python t/test.py

tftpy/TftpStates.py

@@ -156,6 +156,7 @@ class TftpContext(object):
                 continue
             break
         else:
+            self.sock.close()
             raise TftpException, "Hit max timeouts, giving up."
 
         # Ok, we've received a packet. Log it.