preload: simplify by using scanner options
preload: simplify by using scanner options

Use scanner.MatchAll and scanner.ScannerOptions.PrecertOnly

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