DS installers check for open ports has multiple issues:

• ipaserver.install.dsinstance.check_ports uses not host_port_open(...). The function returns False when it cannot connect a server on IPv4 and IPv6 of all IP addresses. This means that the check will pass if only e.g. IPv4 port is in use, see #7415.
• The check uses None as hostname, which translates to IP address of localhost. However a port can be bound to one interface. The check should validate all available IP addresses.
• check_dirsrv function exists two times, one in install and another time in replicainstall.
• install_replica_ds just calls dsinstance.check_ports() but the check_ports() function doesn't raise an exception in case the ports are in use.