Before this change, the host given out to clients to connect to a Remote
Process Group Input Port is the host where the NiFi instance runs.
However, sometimes the binding host is different from the host that
clients connect to. For example, when a NiFi instance runs inside a
Docker container, a client on a separate machine must connect to the
Docker host which forwards the connection to the container.
Add a configuration property to specify the host name to give out to
clients to connect to a Remote Process Group Input Port. If the property
is not configured, then give out the name of host running the NiFi
instance.