Fix DnsRecord.get_unique()
Fix DnsRecord.get_unique()

Do not pass options specific to DnsRecord subclasses (like "target" for
SvnRecord) to Fqdn.get_unique()

Reviewed-By: Priya Joshi <3c6cfa6f57440adfc837c4ad04483313acbc2582@morganstanley.com>

stdweird/aquilon,guillaume-philippon/aquilon,quattor/aquilon,quattor/aquilon,quattor/aquilon,stdweird/aquilon,guillaume-philippon/aquilon,stdweird/aquilon,guillaume-philippon/aquilon