manifests/jenkins-s2i: set scheduled on our imagestreams

I'm not sure why we didn't do this before. Without this, the
imagestreams are only updated manually. In the `jenkins-with-cert`
flow, we already have an `ImageChange` trigger which ensures that
`jenkins:latest` is kept fresh. So this change is putting the non-
custom-cert path at parity.

Note that this is separate from starting and deploying the S2I build,
which currently is still done manually.

Author: jlebon

manifests/jenkins-s2i.yaml

@@ -57,6 +57,8 @@ objects:
             namespace: openshift
           referencePolicy:
             type: Source
+          importPolicy:
+            scheduled: true
   - kind: BuildConfig
     apiVersion: v1
     metadata:
@@ -103,3 +105,5 @@ objects:
             namespace: openshift
           referencePolicy:
             type: Source
+          importPolicy:
+            scheduled: true