fix metric naming test (#4017)
fix metric naming test (#4017)

Signed-off-by: Ben Ye <730e4ef81dca03ba0c5a00c612d6b33341278a96@gmail.com>
coredns/coredns,johnbelamaric/coredns,johnbelamaric/coredns,chrisohaver/coredns,miekg/coredns,yongtang/coredns,miekg/coredns