Bluetooth: host: Fix indicate without user callback

Fix indicate without func not working properly, when sent as a
non-req by GATT this has two propblems:
 - The indicate would not be treated as a transaction, and back
   to back indicate would be sent without waiting for the confirm
 - The destroy callback would not be called on the indicate parameters
   since the indicate_rsp callback would not be called.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>