Made the acceptance test template more Windows friendly.
(cherry picked from commit c1cf05a1984980c5fda172454679deb415de70cb)
Don't return FNCALL_FAILURE in FnCallReturnsZero.

While it might seem more correct, for "returnszero()" it has the
unintended side effect of making this policy

  classes:
    "commandfailed" not => returnszero("/bin/nosuchcommand", "noshell");

not set the "commandfailed" class. This happens because FNCALL_FAILURE
will never set *any* class, regardless of the negation used.
wip