Perfect forwarding on async_method_call

In this code, there was clearly an attempt to implement perfect
forwarding, given that this is just an intermediate function.

Implement perfect forwarding.

Change-Id: I62abfa2d85aad73dcb45eaf0cbf81a26cabdcb03
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/include/sdbusplus/asio/connection.hpp b/include/sdbusplus/asio/connection.hpp
index eeac342..9a75b5c 100644
--- a/include/sdbusplus/asio/connection.hpp
+++ b/include/sdbusplus/asio/connection.hpp
@@ -205,10 +205,11 @@
     void async_method_call(MessageHandler&& handler, const std::string& service,
                            const std::string& objpath,
                            const std::string& interf, const std::string& method,
-                           const InputArgs&... a)
+                           InputArgs&&... a)
     {
         async_method_call_timed(std::forward<MessageHandler>(handler), service,
-                                objpath, interf, method, 0, a...);
+                                objpath, interf, method, 0,
+                                std::forward<InputArgs>(a)...);
     }
 
 #ifndef SDBUSPLUS_DISABLE_BOOST_COROUTINES