libxl: handle external domain destroy

libxl: handle external domain destroy

If domain is killed with `xl destroy`, libvirt will not notice it and
still report the domain as running. Also trying to destroy the domain
through libvirt will fail. The only way to recover from such a situation
is to restart libvirt daemon. The problem is that even though libxl
report LIBXL_EVENT_TYPE_DOMAIN_DEATH, libvirt ignore it as all the
domain cleanup is done in a function actually destroying the domain. If
destroy is done outside of libvirt, there is no place where it would be
handled.

Fix this by doing domain cleanup in LIBXL_EVENT_TYPE_DOMAIN_DEATH too.
To avoid doing it twice, add a ignoreDeathEvent flag
libxlDomainObjPrivate, set when the domain death is triggered by libvirt
itself.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>