Since the cert pair is written with a subsequent call to
cert.WriteCertPair we can safely remove the two file paths from the
argument list of cert.GenCertPair.
This adds in a new boolean flag that when set, prevents LND from writing the system hostname and network interface IPs to the TLS certificate. This will ensure privacy for those that don't want private IP addresses to be exposed on a public facing LND node.
This commit creates a new utility method IsOutdated that can be used to
check whether a TLS certificate mathces the extra IPs and domains given
in the lnd config.
