increasing build timeout on siab job. sometimes when tests fail, it will take longer as many steps require polling of object states

Change-Id: I0b9313ae09a7bdbbe4c3044048e6a28965fc5bff
diff --git a/jjb/siab-e2e.yaml b/jjb/siab-e2e.yaml
index 31664ee..0ff1f83 100644
--- a/jjb/siab-e2e.yaml
+++ b/jjb/siab-e2e.yaml
@@ -7,7 +7,7 @@
     refspec: 'refs/heads/master'
     failure-email-address: 'andy@opennetworking.org'
     timed-trigger: '{every-hour}'
-    build-timeout: 20
+    build-timeout: 60
     jobs:
       - 'siab-e2e-att'