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>
When we have an external component that checks /health periodically, the
etcd server logs can be quite verbose (e.g., DDOS-ing against insure
etcd health check can lead to disk space full due to large log files).
This change was introduced in #11704.
While we keep the warning logs for etcd health check failures, the
success (or OK) log level should be set to DEBUG.
Fixes#12676