Add/clarify cache key tests.
Add/clarify cache key tests.

The test meaning to test changes in server ports was also changing the
host, so it wasn't a great test of just changing the port. So fix that,
and then add some other tests to test other variations of host/ports
combinations.

NREL/api-umbrella,NREL/api-umbrella,NREL/api-umbrella,NREL/api-umbrella