ParserTests: Reset editMode before each html2wt conversion.

* In 324865ba, I added an editMode option but didn't properly
  clone the environment before modifying it.  This in turn
  affected the results of wt2wt tests when running alongwith
  selser.

* For now, I turned off the incorrect cloning and am resetting
  the flag before each test.  This seems like a temporary fix.

* wt2wt results are now identical with/without selser on.

Change-Id: Idb4b530d227b385233b9131f3ac68aab06f72ab2
Merge "ParserTests: Reset editMode before each html2wt conversion."