Rename irc-meetings index.html in job logs

Having the uploaded artifact "index.html" conflict with the file
index served for logs can cause some very confusing results. Make
sure this does not happen.

Change-Id: I6e76eb4009344fbb266a3d2909887682c87131b5

jenkins/jobs/infra.yaml

@@ -145,5 +145,13 @@
           envlist: 'ical'
 
     publishers:
+      - postbuildscript:
+          builders:
+            - shell: |
+                #!/bin/bash -x
+                # We don't want this file to conflict with the log index
+                if test -f output/index.html; then
+                    mv output/index.html output/site-index.html
+                fi
       - zuul-swift-upload-logs-with-console:
           upload_source: 'output/*'