Add doc root markers to infra publications

These infra publications don't get root markers in their top level dirs,
the marker goes into the dir above them which results in the
publications getting removed. Reorder some things in the job so that the
marker is dropped first then copied where it needs to go thus preserving
these publications.

Change-Id: I947137f99b7fd552e46bdcecc7ce46fcffcc59a5

jenkins/jobs/infra-publications.yaml

@@ -7,6 +7,8 @@
       - gerrit-git-prep
       - install-distro-packages
       - revoke-sudo
+      - add-docs-root-marker:
+          docsrootdir: '.'
       - shell: |
           #!/bin/bash -x
           # NAME will either be the branch name or the tag name
@@ -16,9 +18,9 @@
               if [ "_out" != "$FN" ] ; then
                   mv $FN _out/$NAME/
               fi
+          # Explicitly copy the root marker file
+          mv .root-marker _out/$NAME/
           done
-      - add-docs-root-marker:
-          docsrootdir: _out/
 
     publishers:
       - afs: