fix problem 20636 on gforge
- When a permanent receiver was set, the comm->mailbox was copied from
the other comm
- But this is a marker of the which mailbox I'm enrolled into.
- So if I'm not pushed into a mailbox queue, then my mailbox field
must remain clear.
- This problem was probably added during one of the recent
objectification battle.
- It remained undiscovered so far because it seems to appear only when
a second task is added to a permanent_receive mailbox.
This is at least my understanding of the problem, I'm not 100% sure.
