Update endpoint test to use service ids
Update endpoint test to use service ids

This changes the two tests to more closely map to what
we wanted to test when we originally wrote these tests.

These tests were written before serviceId existed, which
is really want we want to use for testing.  These tests check
two things:

* Ensure that the directory names (i.e the client names) match
  the computed name based on the serviceId.  Existing services
  still need overrides but new services shouldn't as many overrides.
* Update the endpoints tests to be more direct about endpoint prefix
  matching.  We really just care that everything in the endpoints.json
  maps to something we can create a client for.  We now build the
  list of acceptable keys by looking up the endpoint prefix.

boto/botocore,pplu/botocore