fix(blade): let a discovery request reach the findme handler

A node that boots sends a findme request to say that it is there. That
request names no node, because the node is what the request asks xCAT to
find. The preprocessor of the blade plugin asks for a noderange for every
command, so it answers "Missing Noderange" with an error code and gives back
no request. The daemon then has nothing to give to the handler, and the
findme handler of the plugin does not run.

The plugin therefore answers each discovery request with an error, and blade
discovery does not happen. The check that asks for a noderange is older than
the findme handler.

Hand a findme request to the handler, as the switch plugin does for the
commands that it does not preprocess. Every other command keeps the check.

The preprocessor also held a test that removed a node from a findme request
when the hardware type was not blade. A findme request now returns above that
test, and it named a noderange that a findme request never carries, so the
test could not run. Remove it.