Fix : LE scanning malfunction

Fix : LE scanning malfunction

[Model] All
[BinType] AP
[Customer] OPEN

[Issue#] N/A
[Request] Internal
[Occurrence Version] N/A

[Problem] APIs execute successfully without any errors, but LE scanning is not working
[Cause & Measure] Before scan stopping is completed, application request LE scan again.
 After receive LEDiscoveryFinished event, trigger LE scanning again.
[Checking Method] Call bt_adapter_le_start_scan() just after calling bt_adapter_le_stop_scan()

[Team] IoT Hub
[Developer] Injun Yang
[Solution company] Samsung
[Change Type] Specification change

Change-Id: I4927f5ba75451bc6f3fb87d758d2f141cc0c2b8d
Signed-off-by: injun.yang <injun.yang@samsung.com>
Signed-off-by: DoHyun Pyun <dh79.pyun@samsung.com>