(Bug 67768) Update TSR when converting invalid wikilinks to plain text

* When invalid wikilinks were being converted to plain text, the right
  TSR was not being set in scenarios where the invalid link content
  came from transclusions/params.

* This patch fixes that bug by adjusting TSR of the DOM-fragment.

* Fixes the inconsistency warnings from DSR computation which also
  corrects the incorrect DSR assignment on the following snippet:

<blockquote>[[{{{1}}}]]</blockquote>abcdefgh

  In turn, this eliminates selser errors when serializing back.

Parser test run changes:
------------------------
* 2 fewer DSR inconsistency warnings (49 --> 47).
* Fixes a rt-selser error on "bug 51090" parser test which is
  actually a very similar scenario as reported in bug 6776.
* Makes selser output more accurate now, and the new failures
  are actually false reports since non-selser test run is less
  accurate when compared to selser.

Change-Id: I4106d19997877cf7c788803d57200e4e38f9d3b9