Fix CircleCI toggle tar pkg test 

https://circleci.com/gh/smallinsky/mtf/325
```
?   	github.com/smallinsky/mtf/pkg/tar	[no test files]
--- FAIL: TestHTTPServer (0.01s)
    http_server_test.go:51: http call failed: Get http://localhost:8080/testpath: dial tcp 127.0.0.1:8080: connect: connection refused
FAIL
FAIL	github.com/smallinsky/mtf/port	0.032s
```
