Bluetooth: fix not setting security level when creating a rfcomm session

This cause 'No Bonding' to be used if userspace has not yet been paired
with remote device since the l2cap socket used to create the rfcomm
session does not have any security level set.

Signed-off-by: Luiz Augusto von Dentz <luiz.dentz-von@nokia.com>
Acked-by: Ville Tervo <ville.tervo@nokia.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>