[test spec] Define general variables for environments

My opinion:
-Better to proliferate these variables throughout the tree than
complicated, space-hungry scopes (which developers will invariably groan
about having to type out). Moreover, these are more easily grep-able.
-If we introduce a second nuc, then we can always rename nuc_env to
dawson_canyon_env; same for vim2 or any other environment.

Bug: IN-497

Change-Id: I54acaa2cee62318be6b7b2bd9ae1a4d33d97d834
2 files changed