Take #2: (Bug 52103) nowiki escaping when quotes surround i/b tags

* Previous attempt (87759dea) overreached by applying previously
  existing checks for HTML nodes to text nodes -- this was buggy
  based on the failure on the example below.

  $ echo "'<span><i>foo</i></span>'" | node parse --html2wt
  '<span><nowiki/>''foo''<nowiki/></span>'

  This requires no <nowiki/> escaping but 87759dea added them.

* Added a parser test to capture this scenario + regenerated
  selser changes.

Change-Id: I0ca644d565cf2790cca918fd7bc9c20dfbc6d29d