vfio/container: Simplify vfio_container_init()

vfio/container: Simplify vfio_container_init()

Assign the base container VFIOAddressSpace 'space' pointer in
vfio_address_space_insert(). The ultimate goal is to remove
vfio_container_init() and instead rely on an .instance_init() handler
to perfom the initialization of VFIOContainerBase.

To be noted that vfio_connect_container() will assign the 'space'
pointer later in the execution flow. This should not have any
consequence.

Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>