ekf_hgt: call specific height reset function instead of generic one

- Also use the delayed current data instead of newest that might not be
available (gps buffer is sometimes empty if the dt between samples is
larger than the delayed horizon).

- Separate "baro fault" from "baro intermittent": intermittent is a
  temporary failure and should prevent from switching to baro right now,
  but "fault" means that it should never be used anymore

- In case of height timeout, check for metrics but not for consistency
  as the filter is likely to have diverged already.

src/modules/ekf2/EKF/gps_checks.cpp

@@ -101,11 +101,6 @@ bool Ekf::collect_gps(const gps_message &gps)
 		_gps_origin_eph = gps.eph;
 		_gps_origin_epv = gps.epv;
 
-		// if the user has selected GPS as the primary height source, switch across to using it
-		if (_params.vdist_sensor_type == VDIST_SENSOR_GPS) {
-			startGpsHgtFusion();
-		}
-
 		_information_events.flags.gps_checks_passed = true;
 		ECL_INFO("GPS checks passed");