Prefer API V2 when a CA directory offers both

[tlhackque]

When working on Apache httpd's mod_md last year, I ran into a CA (name escapes me at the moment) that offers API V1 and V2 in the same directory. (At the same URL.) Since API V1 is deprecated/obsolete, getssl should choose V2 in this case.

Looks like a trivial change - I'll push a patch to my repo, but it could use a test.

[tlhackque]

The CA is BuyPass.

Here's their unified directory case (formatted for readability) - note that the directory has both new-reg and newAccount:

https://api.buypass.com/acme/directory

{"new-reg":"https://api.buypass.com/acme/new-reg",
 "new-cert":"https://api.buypass.com/acme/new-cert",
 "new-authz":"https://api.buypass.com/acme/new-authz",
 "revoke-cert":"https://api.buypass.com/acme/revoke-cert",
 "key-change":"https://api.buypass.com/acme/key-change",
 "meta":{"website":"https://buypass.com/",
 "caa-identities":["buypass.com"],
 "terms-of-service":"https://api.buypass.com/acme/terms/750",
 "caaIdentities":["buypass.com"],
 "termsOfService":"https://api.buypass.com/acme/terms/750"},
 "newNonce":"https://api.buypass.com/acme-v02/new-nonce",
 "newAccount":"https://api.buypass.com/acme-v02/new-acct",
 "newAuthz":"https://api.buypass.com/acme-v02/new-authz",
 "newOrder":"https://api.buypass.com/acme-v02/new-order",
 "revokeCert":"https://api.buypass.com/acme-v02/revoke-cert",
 "keyChange":"https://api.buypass.com/acme-v02/key-change"
}

Documentation: https://community.buypass.com/t/63d4ay/buypass-go-ssl-endpoints-updated-14-05-2020

[tlhackque]

I added a test for this to the PR.