fix version-skew-cajoled tests

the version-skew-cajoled tests don't force es53, so they fail if the
automode decides to use es5. In particular, Safari 6.0.4 passes
the checks well enough that it defaults to es5 mode, so the
version-skew-cajoled tests fail.

[kpreid2, 2013-06-04 17:02:46]

LGTM

I think it would be a nice improvement to have a check that explicitly fails if
inES5Mode is not false ("This test does not apply to ES5 mode"), rather than
silently ignoring that external parameter.

[felix8a, 2013-06-04 19:29:12]

@r5438