Fix trailing whitespace (#4103)
Fix trailing whitespace (#4103)

The latest commit (e233f59) on master branch introduced a trailing
whitespace and is causing Travis CI build to fail:
https://travis-ci.org/github/coredns/coredns/builds/722988413

This PR fixes the failing test.

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>
johnbelamaric/coredns,coredns/coredns,miekg/coredns,chrisohaver/coredns,yongtang/coredns,johnbelamaric/coredns,miekg/coredns