Index screen-c-bak logs for logstash

With the recent ceph gate blocker with backups it'd be good to be able
to query for failures in the cinder backup logs, so let's add it to the
logstash index.

Example log: http://goo.gl/4IIWai

Related-Bug: #1476416

Change-Id: Ie5f63e3a4acb5cfef97292cd7c8a009d86ee703a

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

@@ -56,6 +56,10 @@ source-files:
     tags:
       - screen
       - oslofmt
+  - name: logs/screen-c-bak.txt
+    tags:
+      - screen
+      - oslofmt
   - name: logs/screen-c-sch.txt
     tags:
       - screen
@@ -253,6 +257,11 @@ source-files:
       - screen
       - oslofmt
     job-filter: '.*grenade.*'
+  - name: logs/new/screen-c-bak.txt
+    tags:
+      - screen
+      - oslofmt
+    job-filter: '.*grenade.*'
   - name: logs/new/screen-c-sch.txt
     tags:
       - screen
@@ -379,6 +388,11 @@ source-files:
       - screen
       - oslofmt
     job-filter: '.*grenade.*'
+  - name: logs/old/screen-c-bak.txt
+    tags:
+      - screen
+      - oslofmt
+    job-filter: '.*grenade.*'
   - name: logs/old/screen-c-sch.txt
     tags:
       - screen