Some architectures (s390x) need to cleanup after a failed dump to be
able to continue to run the vm. Add a cleanup function pointer and
call it if it's set.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20231109120443.185979-3-frankja@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>