Bluetooth: Introduce SDK APIs for L2cap socket for Obex over L2cap

Introduce SDK APIs for the L2CAP socket for the obex over l2cap
feature.

The applications whcih uses obex over L2cap feature can make use
of these APIs to create L2cap socket.

CRs-Fixed: 639499
Change-Id: I423ae95ec4e1dc02712609e7c25d2274c5816149
Bluetooth: Adds check to verify Bluetooth adapter state

This checks whether bluetooth is turned ON or not in BLE
start scan process.BLE scan apis are called from applications
so need to check if BT adapter state is ON to avoid Bluetooth
crash

CRs-fixed: 649274
Change-Id: Ic075e1560bba2cabbfac2e1477932f9ad3144067