core: errors on junk in the command line (#744)
core: errors on junk in the command line (#744)

We would silently ignore anything that we couldn't parse on the command
line, this change make this an error.

Fixes #743
coredns/coredns,johnbelamaric/coredns,miekg/coredns,jremond/coredns,yongtang/coredns,johnbelamaric/coredns,ii/coredns,ii/coredns,chrisohaver/coredns,miekg/coredns,jremond/coredns,varyoo/coredns