Retry on busy too fast.

[chrissearle]

Looks like if you try to take a snap while the drone is busy we get the error as the return to the command which will instantly force a retry (since it isn't a timeout) and that means we zip thru the retries pretty much instantly.

Affects AEB especially.

Might need to have special case for: add a pause before retry if the error is busy

Log:

W: 2016/11/07 09:35:06:033 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:151 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:258 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:484 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:584 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:785 [com.apple.main-thread/969896] CameraController takeASnap line: 196 Camera Controller takeASnap - error seen - Error Domain=DJISDKCameraErrorDomain Code=-3002 "Camera is busy or the command is not supported in the camera's current state(code:-3002)" UserInfo={NSLocalizedDescription=Camera is busy or the command is not supported in the camera's current state(code:-3002)} 
W: 2016/11/07 09:35:06:785 [com.apple.main-thread/969896] CameraController takeASnap line: 169 Camera Controller takeASnap - counter exceeds max count - aborting