Enable JJB jobs for istanbul branches

Issue-ID: POLICY-3696
Change-Id: I3ec7a114a70b497c6cef74220240dac3daffa7b6
Signed-off-by: liamfallon <liam.fallon@est.tech>
diff --git a/jjb/policy/policy-common.yaml b/jjb/policy/policy-common.yaml
index 619c343..72042bf 100644
--- a/jjb/policy/policy-common.yaml
+++ b/jjb/policy/policy-common.yaml
@@ -21,6 +21,8 @@
           branch: 'guilin'
       - 'honolulu':
           branch: 'honolulu'
+      - 'istanbul':
+          branch: 'istanbul'
     mvn-settings: 'policy-common-settings'
     java-version: openjdk11
     files: '**'