Bluetooth: SDP: Attempt reuse existing SDP client session

Adds validation check when 'sdp discovery' API is to be called
by client, to reuse existing connection if valid or initiate new one
if posssible to set SDP L2CAP link to remote.

Change-Id: I47ce33cb5e95cf2616f9b23712641b912ce40f37
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>