ipc: ipc_service: Remove the race condition from bonding

This commit removes the possible race condition when notifying
the bonding request.
When the race condition appears there is possibility that
one of the cores would never send notification for bonding.
This change makes it sure that the notification would be sent
at least once.

Signed-off-by: Radoslaw Koppel <radoslaw.koppel@nordicsemi.no>