Copter: fix arming tone to sound before arming

Also fixed bug in which vehicle could appear to be armed (according to
LEDs) but is not.  This could occur if pilot had raised the throttle
very high during the calibration that happens just before arming.

ArduCopter/motors.pde

@@ -130,6 +130,13 @@ static void init_arm_motors()
     // disable inertial nav errors temporarily
     inertial_nav.ignore_next_error();
 
+    // notify that arming will occur (we do this early to give plenty of warning)
+    AP_Notify::flags.armed = true;
+    // call update_notify a few times to ensure the message gets out
+    for (uint8_t i=0; i<=10; i++) {
+        update_notify();
+    }
+
 #if LOGGING_ENABLED == ENABLED
     // start dataflash
     start_logging();
@@ -178,6 +185,8 @@ static void init_arm_motors()
     if (g.rc_3.control_in > g.throttle_cruise && g.throttle_cruise > 100) {
         motors.output_min();
         failsafe_enable();
+        AP_Notify::flags.armed = false;
+        AP_Notify::flags.arming_failed = false;
         return;
     }