Don't infer parsoid-only parser tests based on presence of parsoid option.

Don't infer parsoid-only parser tests based on presence of parsoid option.

For historical reasons, we used a complicated test to try to determine
if a test is "parsoid only" based on the presence of the string "parsoid"
in the parser test options clause.  But really test clauses should be
marked up specifically as html/php or html/parsoid, we don't need to
play hacky games any more.  Remove some unnecessary code and simplify
the test logic.

Change-Id: Ia331e7e12a75aa19aeb96601712f169f2aa75bf9