hack/update-expected.sh: mask development env vars
hack/update-expected.sh: mask development env vars

There are a few env vars which are frequently set in development, but
should not be reflected in the tests.  Clear them before generated the
expected output.

justinsb/kops,robinpercy/kops,justinsb/kops,aledbf/kops,aledbf/kops,kubernetes/kops,aledbf/kops,kubernetes/kops,aledbf/kops,robinpercy/kops,justinsb/kops,robinpercy/kops,kubernetes/kops,robinpercy/kops