MAV_CMD_ARM_AUTHORIZATION_REQUEST - clarify use of progress (mavlink#1965)

Author: hamishwillee

message_definitions/v1.0/common.xml

@@ -2260,7 +2260,9 @@
         <param index="2" label="Immediate">Force immediate transition to the specified MAV_VTOL_STATE. 1: Force immediate, 0: normal transition. Can be used, for example, to trigger an emergency "Quadchute". Caution: Can be dangerous/damage vehicle, depending on autopilot implementation of this command.</param>
       </entry>
       <entry value="3001" name="MAV_CMD_ARM_AUTHORIZATION_REQUEST" hasLocation="false" isDestination="false">
-        <description>Request authorization to arm the vehicle to a external entity, the arm authorizer is responsible to request all data that is needs from the vehicle before authorize or deny the request. If approved the progress of command_ack message should be set with period of time that this authorization is valid in seconds or in case it was denied it should be set with one of the reasons in ARM_AUTH_DENIED_REASON.
+        <description>Request authorization to arm the vehicle to a external entity, the arm authorizer is responsible to request all data that is needs from the vehicle before authorize or deny the request.
+		If approved the COMMAND_ACK message progress field should be set with period of time that this authorization is valid in seconds.
+		If the authorization is denied COMMAND_ACK.result_param2 should be set with one of the reasons in ARM_AUTH_DENIED_REASON.
         </description>
         <param index="1" label="System ID" minValue="0" maxValue="255" increment="1">Vehicle system id, this way ground station can request arm authorization on behalf of any vehicle</param>
       </entry>