ListenHTTP should support inferred Client Authentication

Changes to ListenHTTP in NIFI-1930 and NIFI-8096 introduced a new Client Authentication property to support configuration of whether the processor should request or require client certificates for HTTPS connections.  Prior to these changes, the processor inferred requesting or requiring client certificates based on the absence or presence of trust store properties in the configured SSLContextService. A new default property should be added to the list of Client Authentication options in order to provide backwards compatibility.