The image-reflector controller now accepts a secret containing a
client certificate and key, and/or a CA certificate; so it's useful to
have a command for creating them.
`flux create secret helm` is close, but accepts username/password
(which would be ignored), and has the wrong name of course. Happily
though, much can be shared between the implementations.
Signed-off-by: Michael Bridgen <michael@weave.works>
