platform: delay destruction of NMPlatform singleton until NMConfig gets destroyed

We want to create the platform instance rather late (especially after
claiming the D-Bus service). But we also want to destroy it very late,
because NMPlatform does not make use of any other singletons, but
other singletons make use of NMPlatform.

src/main.c

@@ -420,11 +420,7 @@ main (int argc, char *argv[])
 	/* Set up platform interaction layer */
 	nm_linux_platform_setup ();
 
-	/* FIXME: intentionally leak the singleton instance of NMPlatform.
+	NM_UTILS_KEEP_ALIVE (config, NM_PLATFORM_GET, "NMConfig-depends-on-NMPlatform");
-	 * nm_linux_platform_setup() will register the singleton for destruction,
-	 * but we don't yet shut down all singletons properly, so don't destroy
-	 * NMPlatform. */
-	g_object_ref (NM_PLATFORM_GET);
 
 	nm_dispatcher_init ();