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: I2516cfa21eaf0fc51902f2b23d4a54241e9d4978
diff --git a/extensions/openpower-pels/data_interface.cpp b/extensions/openpower-pels/data_interface.cpp
index 50424af..b812e97 100644
--- a/extensions/openpower-pels/data_interface.cpp
+++ b/extensions/openpower-pels/data_interface.cpp
@@ -268,8 +268,7 @@
 
     auto reply = _bus.call(method, dbusTimeout);
 
-    DBusPathList paths;
-    reply.read(paths);
+    auto paths = reply.unpack<DBusPathList>();
 
     return paths;
 }
@@ -285,8 +284,7 @@
 
     auto reply = _bus.call(method, dbusTimeout);
 
-    std::map<DBusService, DBusInterfaceList> response;
-    reply.read(response);
+    auto response = reply.unpack<std::map<DBusService, DBusInterfaceList>>();
 
     if (!response.empty())
     {
@@ -494,8 +492,7 @@
 
     auto reply = _bus.call(method, dbusTimeout);
 
-    std::string expandedLocationCode;
-    reply.read(expandedLocationCode);
+    auto expandedLocationCode = reply.unpack<std::string>();
 
     if (!connectorLoc.empty())
     {
@@ -532,8 +529,7 @@
 
     auto reply = _bus.call(method, dbusTimeout);
 
-    std::vector<sdbusplus::message::object_path> entries;
-    reply.read(entries);
+    auto entries = reply.unpack<std::vector<sdbusplus::message::object_path>>();
 
     std::vector<std::string> paths;