test: change call to deprecated util.isError()

common.Error() is just util.isError() which is deprecated. Use
assert.throws() instead.

PR-URL: https://github.com/nodejs/node/pull/3084


Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>