Grant administrateCheckers permission to Zuul

Change-Id: Ie6bebd26b5abe2e8daf0940167f8c6a8b7b078dc
diff --git a/groups b/groups
index eb76e03..85b2a2d 100644
--- a/groups
+++ b/groups
@@ -6,3 +6,4 @@
 global:Anonymous-Users                  	Anonymous Users
 global:Project-Owners                   	Project Owners
 global:Registered-Users                 	Registered Users
+user:zuul                               	user/Zuul (zuul)