Consitently use dbus::utility types

This saves about 4k on the binary size

Tested: Redfish service validator passes.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I9546227a19c691b1aecb80e80307889548c0293f
diff --git a/redfish-core/lib/health.hpp b/redfish-core/lib/health.hpp
index c2e40c7..31adf7b 100644
--- a/redfish-core/lib/health.hpp
+++ b/redfish-core/lib/health.hpp
@@ -189,7 +189,7 @@
         std::shared_ptr<HealthPopulate> self = shared_from_this();
         crow::connections::systemBus->async_method_call(
             [self](const boost::system::error_code ec,
-                   const std::vector<std::string>& resp) {
+                   const dbus::utility::MapperGetSubTreePathsResponse& resp) {
                 if (ec || resp.size() != 1)
                 {
                     // no global item, or too many