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: Id36cca2ca362f505ed9f70d30f6665a8c1a62722
diff --git a/occ_manager.cpp b/occ_manager.cpp
index 6b735f7..ed6453c 100644
--- a/occ_manager.cpp
+++ b/occ_manager.cpp
@@ -326,8 +326,8 @@
 {
     namespace fs = std::filesystem;
 
-    sdbusplus::message::object_path o;
-    msg.read(o);
+    auto o = msg.unpack<sdbusplus::message::object_path>();
+
     fs::path cpuPath(std::string(std::move(o)));
 
     auto name = cpuPath.filename().string();