Index cells logs

We've been trying to get the cells job in the check queue passing
consistently and it's been a game of whack-a-mole with regressions, so
when we're trying to debug new failures it'd be super helpful to
actually have logstash for the cells logs.

This adds the cells logs and only indexes them for the cells job(s)
which is the only time they should appear.

Change-Id: Id4450b7cb5d3303f9cb031c3e77fc17cfff97890

modules/openstack_project/files/logstash/jenkins-log-client.yaml

@@ -129,6 +129,16 @@ source-files:
     tags:
       - screen
       - oslofmt
+  - name: logs/screen-n-cell-child.txt
+    tags:
+      - screen
+      - oslofmt
+    job-filter: '.*cells.*'
+  - name: logs/screen-n-cell-region.txt
+    tags:
+      - screen
+      - oslofmt
+    job-filter: '.*cells.*'
   - name: logs/screen-n-cond.txt
     tags:
       - screen