medium: ui_node: Fix handling of default arguments (bnc#889673)

Syncronize the code for some node commands with the documentation,
and allow the node name to be omitted where it makes sense.
medium: ui_node: Require node arg. for node fence|clearstate
Merge pull request #50 from krig/node-clearstate

medium: ui_node: Fix handling of default arguments (bnc#889673)