(maint) Add real case for autosign cert generation test

Nate Wolfe noticed what looks like a copy paste error in my original
ssl/puppet_cert_generate_and_autosign.rb test that was repeating the
cert generate with autosign false and dns_alt_names case for the
autosign true and dns_alt_names case. This commit replaces that with
tests using autosign true, which on master with ca fails, and requires
manual signing with --allow-dns-alt-names flag.