Propagate nicely exceptions from domains

[Calascibetta Romain]

Currently, if a domain has an exception, it just shows the error and never terminate as we can see here:

miou/lib/miou.ml

Lines 1039 to 1047 in 0560a14

 with 
 | Exit -> 
     pool.domains_counter <- pool.domains_counter - 1; 
     Condition.signal pool.condition_all_idle; 
     Mutex.unlock pool.mutex 
 | exn -> 
     Logs.err (fun m -> 
         m "[%a] Got an unexpected error: %S" Domain_uid.pp domain.uid 
           (Printexc.to_string exn)) 

From an user perspective, it's a bit annoying because the application does not stop nicely: dom0 was not informed that a domain terminated with an exception and when it tries to kill them, it will await forever... So it should not difficult and very nice to propagate the exception to dom0 and terminate nicely the program.

[Calascibetta Romain]

Probably fixed by 506c6ff.