Update LE connection interval after GATT connection completed

Update LE connection interval after GATT connection completed

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

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

[Problem] Connection interval 7.5ms maintained
[Cause & Measure] After GATT connection completed, update interval
[Checking Method] gatt connection

[Team] Convergence BT
[Developer] Injun Yang
[Solution company] Samsung
[Change Type] Specification change

Change-Id: Ia48fe3ac6290018631117e322d100d5d194e4cc3
Signed-off-by: injun.yang <injun.yang@samsung.com>
Signed-off-by: Wootak Jung <wootak.jung@samsung.com>