Disable some dialyzer warnings in riakc_pb_socket:process_response/3.

Dialzyer produces errors such as the following because the code checks
for fields containing `undefined` when the spec does not allow it.

riakc_pb_socket.erl:1786: The pattern 'undefined' can never match the type [binary()]

src/riakc_pb_socket.erl

@@ -1701,6 +1701,8 @@ counter_val_options([_ | _Rest], _Req) ->
 -spec process_response(#request{}, rpb_resp(), #state{}) ->
                               {reply, term(), #state{}} |
                               {pending, #state{}}.
+%% Disable "The pattern 'undefined' can never match the type [binary()]" warnings in process_response/3:
+-dialyzer({no_match, process_response/3}).
 process_response(#request{msg = rpbpingreq}, rpbpingresp, State) ->
     {reply, pong, State};
 process_response(#request{msg = rpbgetclientidreq},