NiFi service discovery uses properties which may have templates as values

NiFi service discovery uses configuration properties, which in many cases have template placeholders instead of actual values when retrieved from the Ambari API.

The NiFi team has recommended alternative properties to reference for resolving these values, and making service discovery work in these scenarios.

• Discovery should use the component host name(s) for the host.
• The URL scheme (i.e., http or https) should be based on the nifi.node.ssl.isenabled property defined in nifi-ambari-ssl-config
• The port should be the value of either the nifi.node.port or nifi.node.ssl.port property, depending on the value of the aforementioned nifi.node.ssl.isenabled value.