Bug#729054: bit more info

[Serge Hallyn <serge.hallyn@ubuntu.com>]

I hit the same bug under ubuntu 14.04.  The faulting memory location
tends to change a bit (0x8, 0xd8, 0x88), but in this particular run I
got:

Cannot access memory at address 0x88

#0  dispatcher_send_message (dispatcher=0x88,
message_type=message_type@entry=16, 
    payload=payload@entry=0x7fffffffe190) at dispatcher.c:173

(gdb) p *dispatcher
Cannot access memory at address 0x88

(gdb) up
#1  0x00007ffff199d0dc in red_dispatcher_add_memslot
(dispatcher=<optimized out>, 
    mem_slot=<optimized out>) at red_dispatcher.c:386

This is add, since red_dispatcher_add_memslot is doing

dispatcher_send_message(&dispatcher->dispatcher,
		RED_WORKER_MESSAGE_ADD_MEMSLOT,
		&payload);

but dispatcher_send_message() is getting dispatcher=0x88.  So how did
&v end up with an invalid address?