Fixed computeDSR and findBuilderTags dom pass to start with body

* Starting with document.body eliminates autoInserted* and dsr
  values on html, head, and body nodes.

* Explictly added DSR on body since selective serializer seems to
  require this.

* Changed "ERROR" message about cs/s inconsistency in computeNodeDSR
  to a "WARNING" about the inconsistency so it is less alarming.

* No change in parser tests results.

* Verified changes on a couple of pages with RT testing.

Change-Id: Iec05e0e32663d9f1be997612869104c9121bdbbb