Unbreak `testling -u` on OS X

This fixes two problems that were preventing `testling -u` from working.

1) Need parens with the ternary operator to make it do what you were
actually intending.

2) Check for -u argument first so that the “friendly message” doesn’t
terminate the process early. This bug was introduced here:
https://github.com/substack/testling/commit/9aa50c4bb45bc0fa78ea7aa5d828
d8491a2b891a