Bluetooth: Don't try to confirm locally initiated SMP pairing

In the case that the just-works model would be triggered we only want to
confirm remotely initiated pairings (i.e. those triggered by a Security
Request or Pairing Request). This patch adds the necessary check to the
tk_request function to fall back to the JUST_WORKS method in the case of
a locally initiated pairing.

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