examples/ct: convert tests to Go normal form
examples/ct: convert tests to Go normal form

Make tests table driven to reduce copy-pasta.
Avoid t.Fatalf() where possible.
Canonicalize error messages.

daviddrysdale/certificate-transparency-go,google/certificate-transparency-go,daviddrysdale/certificate-transparency-go,RJPercival/certificate-transparency-go,daviddrysdale/certificate-transparency-go,RJPercival/certificate-transparency-go,RJPercival/certificate-transparency-go,google/certificate-transparency-go,google/certificate-transparency-go