Plane: use baro healthy()

Use baro last update time in place of healthy to determine whether HIL
sensor updates have started

ArduPlane/GCS_Mavlink.pde

@@ -216,7 +216,7 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan)
         // AHRS subsystem is unhealthy
         control_sensors_health &= ~MAV_SYS_STATUS_AHRS;
     }
-    if (barometer.healthy) {
+    if (barometer.healthy()) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_ABSOLUTE_PRESSURE;
     }
     if (g.compass_enabled && compass.healthy(0) && ahrs.use_compass()) {

ArduPlane/system.pde

@@ -456,8 +456,8 @@ static void check_short_failsafe()
 static void startup_INS_ground(bool do_accel_init)
 {
 #if HIL_MODE != HIL_MODE_DISABLED
-    while (!barometer.healthy) {
-        // the barometer becomes healthy when we get the first
+    while (barometer.get_last_update() == 0) {
+        // the barometer begins updating when we get the first
         // HIL_STATE message
         gcs_send_text_P(SEVERITY_LOW, PSTR("Waiting for first HIL_STATE message"));
         delay(1000);

ArduPlane/test.pde

@@ -578,7 +578,7 @@ test_pressure(uint8_t argc, const Menu::arg *argv)
     while(1) {
         delay(100);
 
-        if (!barometer.healthy) {
+        if (!barometer.healthy()) {
             cliSerial->println_P(PSTR("not healthy"));
         } else {
             cliSerial->printf_P(PSTR("Alt: %0.2fm, Raw: %f Temperature: %.1f\n"),