• The MDCertificateAuthority directive can take more than one URL/name of
  an ACME CA. This gives a failover for renewals when several consecutive attempts
  to get a certificate failed. See REAME for details.
• New directive MDRetryDelay to set the delay of retries. See README
  for details.
• New directive MDRetryFailover to set the number of errored attempts
  before an alternate CA is selected for certificate renewals. See README
  for details.