commander arming_state_transition: do not call prearm_check if !fRunPreArmChecks

Reason: if you don't want preflight checks, you don't want prearm checks
either (these are the circuit breakers, like usb connected check).

The other changes are cleanup and rework of operations.

In most cases, arming_state_transition is called with fRunPreArmChecks set
to true, so no change in behavior.

The cases with fRunPreArmChecks=false are:
- unit tests
- in_arming_grace_period=true (quick arming after disarm)
- VEHICLE_CMD_PREFLIGHT_CALIBRATION (does not transition to armed)

src/modules/commander/state_machine_helper.cpp

@@ -119,7 +119,6 @@ transition_result_t arming_state_transition(vehicle_status_s *status, const safe
 		 * Get sensing state if necessary
 		 */
 		bool preflight_check_ret = true;
-		bool prearm_check_ret = true;
 
 		const bool checkGNSS = (arm_requirements & ARM_REQ_GPS_BIT);
 
@@ -162,15 +161,16 @@ transition_result_t arming_state_transition(vehicle_status_s *status, const safe
 
 				//      Do not perform pre-arm checks if coming from in air restore
 				//      Allow if vehicle_status_s::HIL_STATE_ON
-				if (status->arming_state != vehicle_status_s::ARMING_STATE_IN_AIR_RESTORE &&
-				    !hil_enabled) {
+				if (status->arming_state != vehicle_status_s::ARMING_STATE_IN_AIR_RESTORE && !hil_enabled) {
 
-					if (preflight_check_ret) {
+					bool prearm_check_ret = true;
+
+					if (fRunPreArmChecks && preflight_check_ret) {
 						// only bother running prearm if preflight was successful
 						prearm_check_ret = prearm_check(mavlink_log_pub, *status_flags, safety, arm_requirements);
 					}
 
-					if (!(preflight_check_ret && prearm_check_ret)) {
+					if (!preflight_check_ret || !prearm_check_ret) {
 						// the prearm and preflight checks already print the rejection reason
 						feedback_provided = true;
 						valid_transition = false;