Removed unused node variable.

Removed unused node variable.

The node is now calculated by read_state and in the state
structure.  The node could be reset by re-initializing
the state or calling the read state function.  Given that
the mac address is just used to provide additional uniqueness
its actual value doesn't really matter, so assuming it
wasn't just a bunch of zeroes or similar, there shouldn't
be any reason to re-determine it.