Adding a child node with an invalid usage should throw an error

[WhoBrokeTheBuild]

Affiliation
PSFC

Description
When adding a child node with an invalid usage (not structure or subtree), it should throw an error. Currently, it silently changes the usage to structure.

Example

TCL> add node .a /usage=numeric
TCL> dir /full .a

\MYTREE::TOP

  A           
      Status: on,parent is on, usage structure
      compress on put
      Data inserted:                            Owner: uid=0(root)
      There is no data stored for this node

Additional context
Found while reviewing #3015