system_configuration: Fix new hostname updates

This allows changes outside of phosphor-networkd to be processed and
handled correctly.

Change-Id: I0bb8e90fe502a6d69f451a45cfecbee1bc89eb66
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/system_configuration.hpp b/src/system_configuration.hpp
index 6bbb83f..b3d91d3 100644
--- a/src/system_configuration.hpp
+++ b/src/system_configuration.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <sdbusplus/bus.hpp>
+#include <sdbusplus/bus/match.hpp>
 #include <sdbusplus/server/object.hpp>
 #include <stdplus/zstring.hpp>
 #include <string>
@@ -46,13 +47,11 @@
     std::string hostName(std::string name) override;
 
   private:
-    /** @brief get the hostname from the system by doing
-     *         dbus call to hostnamed service.
-     */
-    std::string getHostNameFromSystem() const;
-
     /** @brief Persistent sdbusplus DBus bus connection. */
     sdbusplus::bus_t& bus;
+
+    /** @brief Monitor for hostname changes */
+    sdbusplus::bus::match_t hostnamePropMatch;
 };
 
 } // namespace network