Bluetooth: Fix forcing SMP just-works with no-bonding

Whether we bond or not should not have any impact on the user
interaction model. This patch removes an incorrect fall-back from
JUST_CFM to JUST_WORKS in case we're not bonding.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>