Fix Control API on separate port if specs are empty
Fix Control API on separate port if specs are empty

If Control API bind on separate port, and Tyk Gateways started first
time without any API’s, admin api will not work.

Tests was not failing, because some of the previous tests populate api
specs with test data. But if we run `TestControlListener` alone it will
fail.

nebolsin/tyk,nebolsin/tyk,lonelycode/tyk,nebolsin/tyk,nebolsin/tyk,mvdan/tyk,mvdan/tyk,mvdan/tyk,mvdan/tyk,mvdan/tyk,nebolsin/tyk,lonelycode/tyk,nebolsin/tyk,mvdan/tyk,mvdan/tyk,lonelycode/tyk,mvdan/tyk,nebolsin/tyk,nebolsin/tyk