vlan: Modify create method to return an ObjectPath

This will be nice to have for ipmid so that it can easily figure out the
path of the new vlan object when it creates one.

Change-Id: I6b93c5e64499c0cb9e36e8354eda6089bfd6d6c9
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/network_manager.hpp b/network_manager.hpp
index e2dfea9..edb341f 100644
--- a/network_manager.hpp
+++ b/network_manager.hpp
@@ -56,7 +56,7 @@
     Manager(sdbusplus::bus::bus& bus, const char* objPath,
             const std::string& dir);
 
-    void vLAN(IntfName interfaceName, uint32_t id) override;
+    ObjectPath vLAN(IntfName interfaceName, uint32_t id) override;
 
     /** @brief write the network conf file with the in-memory objects.
      */