http: reset replay_count upon connection

Reset the replay_count upon a successful connection.  It's possible that
we could encounter a situation where we connect successfully but need to
replay a request - for example, a connection and initial request
succeeds without authentication but a subsequent call does require
authentication.  Reset the replay count upon any successful request to
afford subsequent replays room to manuever.

src/transports/http.c

@@ -990,6 +990,7 @@ static int http_connect(http_subtransport *t)
 	t->proxy.stream = proxy_stream;
 	t->server.stream = stream;
 	t->connected = 1;
+	t->replay_count = 0;
 	return 0;
 
 on_error: