use sdbusplus unpack syntax

Rather than defining a variable and then reading it from a message,
sdbusplus also supports directly unpack-ing from the message.  Use
this syntax instead as it is more efficient and succinct.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I23902026dee367a8cbf0c2725725c4ed3ca4d2bb
diff --git a/transporthandler.cpp b/transporthandler.cpp
index d99c754..7bcc696 100644
--- a/transporthandler.cpp
+++ b/transporthandler.cpp
@@ -560,8 +560,8 @@
                                    INTF_VLAN_CREATE, "VLAN");
     req.append(params.ifname, static_cast<uint32_t>(vlan));
     auto reply = bus.call(req);
-    sdbusplus::message::object_path newPath;
-    reply.read(newPath);
+    auto newPath = reply.unpack<sdbusplus::message::object_path>();
+
     params.logicalPath = std::move(newPath);
 }