node_device_udev: Introduce and use `stateShutdownPrepare` and `stateShutdownWait`

node_device_udev: Introduce and use `stateShutdownPrepare` and `stateShutdownWait`

Introduce and use the driver functions for the node state shutdown preparation
and wait. As they're also called in the error/cleanup path of
`nodeStateInitialize`, they must be written in a way, that they can safely be
executed even if not everything is initialized.

In the next commit, these functions will be extended.

Reviewed-by: Jonathon Jongsma <jjongsma@redhat.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>