jenkins: Allow Jenkins to read pod logs

Jenkins needs permission to read pod logs so it can display output from
the JNLP agent if it crashes.

jenkins/jenkins.yaml

@@ -74,6 +74,12 @@ rules:
   - pods/exec
   verbs:
   - '*'
+- apiGroups:
+  - ''
+  resources:
+  - pods/log
+  verbs:
+  - get
 
 ---
 apiVersion: rbac.authorization.k8s.io/v1