Description
===========
Tests the `tls.issuerdn` legacy keyword
Tests the `tls.cert_issuer` new keyword
Both represent TLS/SSL certificate IssuerDN field

PCAP
====
PCAP comes from an [existing TLS test](https://github.com/OISF/suricata-verify/blob/master/tests/tls/tls-cert-issuer/tls.pcap)

Redmine ticket
==============
https://redmine.openinfosecfoundation.org/issues/5544
