bumping stable version to 2.2.0b3

Change-Id: I1e4653e58ac12aa6053f46a885b943997ae469cc
diff --git a/jobs.yaml b/jobs.yaml
index 0798378..e7bc057 100644
--- a/jobs.yaml
+++ b/jobs.yaml
@@ -44,7 +44,7 @@
     flavor:
       - trusty32server
       - trusty64server
-    branch: '2.2.0b2'
+    branch: '2.2.0b3'
     tag: '-stable'
     jobs:
       - 'mininet-{flavor}{tag}'