Jenkins: don't build in system mode

--- a/src/Pure/Admin/ci_profile.scala	Fri Oct 14 22:45:29 2016 +0200
+++ b/src/Pure/Admin/ci_profile.scala	Sat Oct 15 10:45:55 2016 +0200
@@ -27,7 +27,7 @@
         max_jobs = jobs,
         dirs = include,
         select_dirs = select,
-        system_mode = true,
+        system_mode = false,
         selection = select_sessions _)
     }
     val end_time = Time.now()