When AIO context is set up kernel does two things:

1. creates an in-kernel aioctx object
2. maps a ring into process memory

The 2nd thing gives us all the needed information
about how the AIO was set up. So, in order to dump
one we need to pick the ring in memory and get all
the information we need from it.

One thing to note -- we cannot dump tasks if there
are any AIO requests pending. So we also need to
go to parasite and check the ring to be empty.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>