utils/ci-test: skip format checks with SKIP_LINT
utils/ci-test: skip format checks with SKIP_LINT

To be more consistent. Now when SKIP_LINT is true, only the tests are
run. This is all we want from the previous Go version, really. The
latest is enough to check gofmt and goimports.

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