test: remove FIXME pummel/test-tls-securepair-client

Reverts: 85827bde
Using `common.PORT` no longer causes other tests to fail

Refs: https://github.com/nodejs/node/issues/4640
PR-URL: https://github.com/nodejs/node/pull/8757


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>