do not check success? but compare exitstatus to 0

I don't understand why there are failures at
https://travis-ci.org/opscode/chef/builds/24999572 which say that
status does not have a success? method.  I'm mostly confused by the
suggestion that status is a Double and not a
Process::Status.  Probably I'm too green.

Anyway, this just changes the comparison to be against 0, not > 1.