Allow nodeup (and others) to replace in-use files
Allow nodeup (and others) to replace in-use files

By creating a tempfile and then moving the file into place, we both
write more atomically and we can overwrite in-use files.

Issue #10122

kubernetes/kops,justinsb/kops,kubernetes/kops,justinsb/kops,kubernetes/kops,justinsb/kops