commander: strengthen pre-flight fail checking

The commander checks use instantaneous values which are vulnerable to false negatives  or positives with noisy data or transient faults.

This patch checks the estimators published pre flight check status which is based on persistent checks using filtered data.

src/modules/commander/PreflightCheck.cpp

@@ -502,6 +502,12 @@ static bool ekf2Check(orb_advert_t *mavlink_log_pub, bool optional, bool report_
 		goto out;
 	}
 
+	// Check if preflight check perfomred by estimator has failed
+	if (status.pre_flt_fail) {
+		success = false;
+		goto out;
+	}
+
 	// check vertical position innovation test ratio
 	param_get(param_find("COM_ARM_EKF_HGT"), &test_limit);
 	if (status.hgt_test_ratio > test_limit) {