Fix the problem that can't add a device from next time once add_device_failed.

Fix the problem that can't add a device from next time once add_device_failed.

- Problem: Once add_device failed, we can't add the device anymore.
- Cause: The request stored in the internal queue is not deleted.
- Solution: If the request is not processed for a certain period of time,
  remove the request from the queue

Change-Id: Ib01d89f687a65715f7a1a51db1ed63c426386776
Signed-off-by: saerome.kim <saerome.kim@samsung.com>