crypto/tls: tests prefer constants to opaque literals
crypto/tls: tests prefer constants to opaque literals

This is minor cleanup that makes the tests more readable.

Change-Id: I9f1f98f0f035096c284bdf3501e7520517a3e4d9
Reviewed-on: https://go-review.googlesource.com/19993
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

momchil-velikov/go,nawawi/go,4ad/go,binarycrusader/go,nawawi/go,CAFxX/go,Cofyc/go,cloudflare/go,linux-on-ibm-z/go,mwhudson/go,vanloswang/go,derekmarcotte/go,theif519/go,goodlang/good,polyverse-security/go,nawawi/go,vanloswang/go,golang/go,ganboing/go-esx,vanloswang/go,binarycrusader/go,vsekhar/elastic-go,josharian/go,theif519/go,Samurais/go,4ad/go,linux-on-ibm-z/go,ImJasonH/go,miolini/go,miolini/go,Cofyc/go,theif519/go,CAFxX/go,ganboing/go-esx,polyverse-security/go,nawawi/go,binarycrusader/go,golang/go,miolini/go,ImJasonH/go,polyverse-security/go,vsekhar/elastic-go,goodlang/good,linux-on-ibm-z/go,ganboing/go-esx,Samurais/go,ImJasonH/go,vsekhar/elastic-go,binarycrusader/go,linux-on-ibm-z/go,momchil-velikov/go,ganboing/go-esx,polyverse-security/go,miolini/go,golang/go,4ad/go,vanloswang/go,Cofyc/go,josharian/go,nawawi/go,4ad/go,vsekhar/elastic-go,josharian/go,Samurais/go,cloudflare/go,CAFxX/go,4ad/go,suncycheng/go,ImJasonH/go,codestation/go,vanloswang/go,ImJasonH/go,golang/go,4ad/go,golang/go,Samurais/go,codestation/go,vanloswang/go,CAFxX/go,derekmarcotte/go,binarycrusader/go,vsekhar/elastic-go,derekmarcotte/go,Cofyc/go,linux-on-ibm-z/go,momchil-velikov/go,theif519/go,derekmarcotte/go,theif519/go,cloudflare/go,josharian/go,nawawi/go,Cofyc/go,mwhudson/go,goodlang/good,Cofyc/go,cloudflare/go,miolini/go,suncycheng/go,cloudflare/go,theif519/go,josharian/go,CAFxX/go,miolini/go,Cofyc/go,ImJasonH/go,mwhudson/go,momchil-velikov/go,nawawi/go,vsekhar/elastic-go,suncycheng/go,codestation/go,miolini/go,mwhudson/go,Samurais/go,Samurais/go,linux-on-ibm-z/go,josharian/go,derekmarcotte/go,goodlang/good,binarycrusader/go,goodlang/good,suncycheng/go,CAFxX/go,vanloswang/go,polyverse-security/go,polyverse-security/go,goodlang/good,ganboing/go-esx,goodlang/good,binarycrusader/go,derekmarcotte/go,akutz/go,mwhudson/go,golang/go,4ad/go,cloudflare/go,Samurais/go,nawawi/go,josharian/go,theif519/go,polyverse-security/go,mwhudson/go,suncycheng/go,golang/go,codestation/go,4ad/go,josharian/go,polyverse-security/go,akutz/go,cloudflare/go,suncycheng/go,CAFxX/go,derekmarcotte/go,codestation/go,mwhudson/go,akutz/go,theif519/go,miolini/go,suncycheng/go,codestation/go,ganboing/go-esx,vanloswang/go,vsekhar/elastic-go,akutz/go,Cofyc/go,mwhudson/go,derekmarcotte/go,ganboing/go-esx,momchil-velikov/go,akutz/go,suncycheng/go,ganboing/go-esx,cloudflare/go,akutz/go,golang/go,codestation/go,ImJasonH/go,momchil-velikov/go,momchil-velikov/go,goodlang/good,CAFxX/go,codestation/go,momchil-velikov/go,akutz/go,linux-on-ibm-z/go,ImJasonH/go,christopher-henderson/Go,akutz/go,vsekhar/elastic-go,Samurais/go,binarycrusader/go,linux-on-ibm-z/go