REST: Add missing return statement

Add a missing return statement to convertJsonToDbus.

The function did appear to still work before, but it
fixes a compile warning.

Change-Id: Ib6b15c822fa6b56c9d9fdaca704bc9c53024fa76
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/include/openbmc_dbus_rest.hpp b/include/openbmc_dbus_rest.hpp
index fb23a8b..f1dbdaf 100644
--- a/include/openbmc_dbus_rest.hpp
+++ b/include/openbmc_dbus_rest.hpp
@@ -748,6 +748,8 @@
             jIt++;
         }
     }
+
+    return r;
 }
 
 void findActionOnInterface(std::shared_ptr<InProgressActionData> transaction,