qemu: Report domain name in unexpectedly closed monitor message

qemu: Report domain name in unexpectedly closed monitor message

When QEMU closes the monitor suddenly, the following error
message is reported:

  internal error: qemu unexpectedly closed the monitor: ...

And this works. But other error messages produced in the same
function include domain name too. Do that for the unexpectedly
closed monitor message too.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>