loadparm: fix process_registry_shares() when there is only [global] in registry.

This fixes testparm printing "Error loading services." when there is only
the global section in registry and no other service definition.

Michael
(This used to be commit 28d1972200)

source3/param/loadparm.c

@@ -6591,6 +6591,8 @@ static bool process_registry_shares(void)
 		goto done;
 	}
 
+	ret = true;
+
 	for (count = 0; count < num_shares; count++) {
 		if (strequal(service[count]->name, GLOBAL_NAME)) {
 			continue;