Added optional TLS min/max protocol version and command line switches to set
versions for the etcd server.
If max version is not explicitly set by the user, let Go select the max
version which is currently TLSv1.3. Previously max version was set to TLSv1.2.
Signed-off-by: Tero Saarni <tero.saarni@est.tech>
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>