Bluetooth: Fix socket not getting freed if l2cap channel create fails

If l2cap_chan_create() fails then it will return from l2cap_sock_kill
since zapped flag of sk is reset.

Signed-off-by: Jaganath Kanakkassery <jaganath.k@samsung.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>