Have stolon work with client certs

[sebasmannem]

Hi,
I want to use stolon with client certs.
That would be other clients, but stolon as well.
I noticed that --pg-su-auth-method, and --pg-repl-auth-method don't support a cert value, that is easilly fixed.
But I also noticed that the first columns for their hba lines are always host and they shoulb be hostssl Making them configurable too is another small and easy addition.
After that I think it will work with using client certs for stolon.
I will also add some documentation.

What would you like to be added:
The option for stolon to communicate with client certificates.

Why is this needed:
For high security environments this is a much appreciated capability.

[sebasmannem]

I will do some preliminary tests and issue a PR.
Just wanted all to know that I will be working on this.