This is a small preparation step for the next patch.
It just renames the key/value constants for the unit
test of MakeLegacyNodeInfo, because they were rather
undescriptive and thus made changes to the test cumbersome.

Signed-off-by: Helga Velroyen <helgav@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>