Bluetooth: controller: fix procedure collision handling

If an instant based remote procedure 'overtakes' a local ditto
the local procedure will be 'completed' by remote rejection
but collision flag would not get set ensuring that a new local
conflicting procedure cannot be started before the remote is completed.
This can thus lead to invalid local initiation.

Added unittest to cover case

Fix by ensuring collision flag is set also in the above mentioned
scenario.

Signed-off-by: Erik Brockhoff <erbr@oticon.com>