[amber] Use full component URI for system_updater

Test: fx ota
CF-156

Change-Id: Iee7a4648e40eb92bee50591eaf0eddbf56c4af6e
diff --git a/go/src/amber/sys_update/sys_update.go b/go/src/amber/sys_update/sys_update.go
index fb3d430..7c30179 100644
--- a/go/src/amber/sys_update/sys_update.go
+++ b/go/src/amber/sys_update/sys_update.go
@@ -148,7 +148,7 @@
 				When:      start,
 			})
 
-			launchDesc := sys.LaunchInfo{Url: "system_updater"}
+			launchDesc := sys.LaunchInfo{Url: "fuchsia-pkg://fuchsia.com/system_updater#meta/system_updater.cmx"}
 			if err := runProgram(launchDesc); err != nil {
 				log.Printf("sys_upd_mon: updater failed to start: %s", err)
 			}