Fix RPCTimerInterface ordering issue

Dispatching a QThread from a non Qt thread is not allowed. Always use the HTTPRPCTimerInterface (non QT) to dispatch RPCRunLater threads.

src/rpcserver.cpp

@@ -563,7 +563,7 @@ void RPCRunLater(const std::string& name, boost::function<void(void)> func, int6
     if (timerInterfaces.empty())
         throw JSONRPCError(RPC_INTERNAL_ERROR, "No timer handler registered for RPC");
     deadlineTimers.erase(name);
-    RPCTimerInterface* timerInterface = timerInterfaces[0];
+    RPCTimerInterface* timerInterface = timerInterfaces.back();
     LogPrint("rpc", "queue run of timer %s in %i seconds (using %s)\n", name, nSeconds, timerInterface->Name());
     deadlineTimers.insert(std::make_pair(name, boost::shared_ptr<RPCTimerBase>(timerInterface->NewTimer(func, nSeconds*1000))));
 }