Copter: relax altitude check in verify_takeoff

Previously we checked if the alt > target_alt but because there is
little to no overshoot with the new accel based alt controller this
check was failing for some users.

ArduCopter/commands_logic.pde

@@ -364,7 +364,7 @@ static bool verify_takeoff()
         return false;
     }
     // are we above our target altitude?
-    return (current_loc.alt > next_WP.alt);
+    return (alt_change_flag == REACHED_ALT);
 }
 
 // verify_land - returns true if landing has been completed