examples/ct: use helper function for chain compare
examples/ct: use helper function for chain compare

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