FanLinc fan speed state updates don't send MQTT

[TD22057]

When FanLinc receives a state update, it only sends the on/off state update and doesn't update the fan speed state.

mosquitto_pub -t 'insteon/aa.bb.cc/fan/speed/set' -m 'low'
yields:
   insteon/aa.bb.cc/fan/speed/set low
   insteon/aa.bb.cc/fan/state ON

Reported by @masterdka

[TD22057]

The bug is that the fanlinc mqtt class was using the dimmer template data generator so the fan speed was never set. The mqtt template then got a null payload since the payload is level_str which was null which skipped the publishing. I've fixed it to use the right template data method and it now publishes these messages:

mosquitto_pub -t 'insteon/aa.bb.cc/fan/speed/set' -m 'low'
yields:
   insteon/aa.bb.cc/fan/speed/set low
   insteon/aa.bb.cc/fan/state ON
   insteon/aa.bb.cc/fan/speed/state low