hw/vfio/container: Fix SIGSEV on vfio_container_instance_finalize()

hw/vfio/container: Fix SIGSEV on vfio_container_instance_finalize()

In vfio_connect_container's error path, the base container is
removed twice form the VFIOAddressSpace QLIST: first on the
listener_release_exit label and second, on free_container_exit
label, through object_unref(container), which calls
vfio_container_instance_finalize().

Let's remove the first instance.

Fixes: 938026053f4 ("vfio/container: Switch to QOM")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>