WATM — Recovery_request needs a failure indication

In Access Recovery to a new Access Bridge (section 8.4.2) the
invocation of recovery_request at the old Access Bridge is assumed to
succeed. However, it is possible that the old tunnel has been down
for so long that the old Access Bridge has destroyed all information
it has on the terminal. This would make it impossible to fill the out
parameter of recovery_request correctly. I therefore suggest that an
exception to signal a destroyed association (possibly TerminalNotHere)
be added to recovery_request signature and that the new Access
Bridge's actions when receiving this exception be specified.

see above