Maxscale Listener should support SSL and unsecured connections

The Mariadb database listener allows SSL and unsecured connections on the same port.

Maxscale does not allow SSL and unsecured connections on the same port.

Documentation is clear on this:
https://mariadb.com/kb/en/mariadb-maxscale-2402-maxscale-2402-mariadb-maxscale-configuration-guide/#tlsssl-encryption
which states:
"Note: MaxScale does not allow mixed use of TLS/SSL and normal connections on the same port."

There should be a way allow mixed use so that the listener can match what the database offers. Example

SSL=TRUE

SSL=FALSE

SSL=MIXED