vici: Fix type error exception in Python bindings

Line 66 yields "TypeError: can't concat bytes to str" using Python 3.4.
"requestdata" was introduced in 22f08609f1 but is not actually used.
Since the original "request" is not used anywhere else this can be changed
to be similar to the other UTF-8 encoding changes in that commit.

Fixes: 22f08609f1 ("vici: Explicitly set the Python encoding type").
Closes strongswan/strongswan#66.

src/libcharon/plugins/vici/python/vici/protocol.py

@@ -62,7 +62,7 @@ class Packet(object):
 
     @classmethod
     def _named_request(cls, request_type, request, message=None):
-        requestdata = request.encode("UTF-8")
+        request = request.encode("UTF-8")
         payload = struct.pack("!BB", request_type, len(request)) + request
         if message is not None:
             return payload + message