Move getProperty calls to utility

Having all dbus calls run through the same utility reduces the amount of
generated code, and more importantly, gives us a place where we can log
the requests and responses to help with debugging.

Tested: Redfish service validator passes.

Change-Id: Ic1bf45130b5069cd57f7af26e12c8d3159c87c67
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/redfish-core/lib/roles.hpp b/redfish-core/lib/roles.hpp
index c17a225..d663ce3 100644
--- a/redfish-core/lib/roles.hpp
+++ b/redfish-core/lib/roles.hpp
@@ -133,8 +133,7 @@
                 asyncResp->res.jsonValue["Name"] = "Roles Collection";
                 asyncResp->res.jsonValue["Description"] = "BMC User Roles";
 
-                sdbusplus::asio::getProperty<std::vector<std::string>>(
-                    *crow::connections::systemBus,
+                dbus::utility::getProperty<std::vector<std::string>>(
                     "xyz.openbmc_project.User.Manager",
                     "/xyz/openbmc_project/user",
                     "xyz.openbmc_project.User.Manager", "AllPrivileges",