The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
As Azure doesn't allow "/" in label keys, we used to convert "/" to
"_", but we didn't convert back "_" to "/" in kops-controller.
Change the code to store a label key in a tag value so that we don't
need to worry about escaping.