wrong number of args with cli flag

Was playing with this and noticed it didn't compile.
Error: `vulcand-auth/auth/auth.go:84: too few values in struct initializer`

Looks like [a breaking change was made upstream](https://github.com/mailgun/vulcand/commit/8bf2e4235081533d297135fb8b462f98a4bd069b#diff-a9fc59ffe86918ec8fc644c65d622c2bR110) and not updated here.