Bug fix serializing wiki elements nested in html elements

* The following wikitext snippet would not serialize the newly
  inserted wikilink as [[Foo]].  It would instead serialize into
  a HTML a-tag instead.

<small data-parsoid="{&quot;stx&quot;:&quot;html&quot;}"><a rel="mw:WikiLink" href="Foo">Foo</a></small>

* Reduced test case based on the following bug report in /mnt/bugs on
  parsoid.wmflabs.org

  2013-06-03T09%3A48%3A14.774Z-Le_Prix_du_silence_(film%252C_2008)

* No change in parser test results
  TODO: html2wt tests needed for new content

Change-Id: I7f9b7cf4dd7c1fadaa48ea99f3f1e19a5190afd6
Merge "Bug fix serializing wiki elements nested in html elements"