cmd/go: for go get -insecure, do not fall back to HTTP for non-200 responses
cmd/go: for go get -insecure, do not fall back to HTTP for non-200 responses

Since we allow non-200 responses from HTTPS in normal operation,
it seems odd to reject them in -insecure operation.

Fixes #13037 (again).

Change-Id: Ie232f7544ab192addfad407525888db6b967befe
Reviewed-on: https://go-review.googlesource.com/17945
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

ganboing/go-esx,cloudflare/go,sndnvaps/go,binarycrusader/go,suncycheng/go,cloudflare/go,mwhudson/go,vsekhar/elastic-go,cyberroadie/go,ganboing/go-esx,cyberroadie/go,cyberroadie/go,binarycrusader/go,roth1002/go,Samurais/go,Samurais/go,akutz/go,binarycrusader/go,suncycheng/go,ImJasonH/go,roth1002/go,theif519/go,mwhudson/go,sndnvaps/go,vanloswang/go,linux-on-ibm-z/go,josharian/go,Endika/go,ImJasonH/go,vsekhar/elastic-go,akutz/go,Cofyc/go,theif519/go,miolini/go,roth1002/go,roth1002/go,goodlang/good,vanloswang/go,akutz/go,Cofyc/go,theif519/go,miolini/go,ganboing/go-esx,theif519/go,momchil-velikov/go,roth1002/go,linux-on-ibm-z/go,cloudflare/go,vanloswang/go,miolini/go,sndnvaps/go,polyverse-security/go,ganboing/go-esx,codestation/go,goodlang/good,suncycheng/go,derekmarcotte/go,linux-on-ibm-z/go,linux-on-ibm-z/go,4ad/go,ganboing/go-esx,nawawi/go,CAFxX/go,theif519/go,theif519/go,Samurais/go,vanloswang/go,nawawi/go,vsekhar/elastic-go,josharian/go,golang/go,Endika/go,vanloswang/go,codestation/go,suncycheng/go,christopher-henderson/Go,nawawi/go,derekmarcotte/go,polyverse-security/go,Cofyc/go,polyverse-security/go,4ad/go,CAFxX/go,polyverse-security/go,ganboing/go-esx,polyverse-security/go,vanloswang/go,Samurais/go,sndnvaps/go,josharian/go,cloudflare/go,derekmarcotte/go,sndnvaps/go,kim-racktop/go,nawawi/go,golang/go,linux-on-ibm-z/go,Cofyc/go,Samurais/go,CAFxX/go,goodlang/good,akutz/go,4ad/go,miolini/go,linux-on-ibm-z/go,codestation/go,4ad/go,CAFxX/go,goodlang/good,josharian/go,kim-racktop/go,kim-racktop/go,CAFxX/go,nawawi/go,roth1002/go,momchil-velikov/go,kim-racktop/go,ImJasonH/go,mwhudson/go,cyberroadie/go,cyberroadie/go,codestation/go,sndnvaps/go,ImJasonH/go,golang/go,ImJasonH/go,josharian/go,polyverse-security/go,golang/go,goodlang/good,codestation/go,mwhudson/go,miolini/go,cyberroadie/go,momchil-velikov/go,cyberroadie/go,josharian/go,vsekhar/elastic-go,4ad/go,suncycheng/go,CAFxX/go,derekmarcotte/go,Endika/go,ganboing/go-esx,ganboing/go-esx,derekmarcotte/go,vanloswang/go,codestation/go,linux-on-ibm-z/go,sndnvaps/go,codestation/go,momchil-velikov/go,Endika/go,codestation/go,mwhudson/go,Cofyc/go,cloudflare/go,Cofyc/go,kim-racktop/go,momchil-velikov/go,theif519/go,kim-racktop/go,nawawi/go,miolini/go,momchil-velikov/go,Endika/go,ImJasonH/go,akutz/go,miolini/go,sndnvaps/go,4ad/go,Cofyc/go,4ad/go,ImJasonH/go,Samurais/go,theif519/go,golang/go,linux-on-ibm-z/go,polyverse-security/go,mwhudson/go,goodlang/good,ImJasonH/go,josharian/go,Endika/go,goodlang/good,akutz/go,Samurais/go,golang/go,mwhudson/go,Endika/go,roth1002/go,vsekhar/elastic-go,golang/go,suncycheng/go,Cofyc/go,momchil-velikov/go,miolini/go,cloudflare/go,binarycrusader/go,momchil-velikov/go,cloudflare/go,golang/go,vsekhar/elastic-go,vsekhar/elastic-go,kim-racktop/go,suncycheng/go,akutz/go,nawawi/go,binarycrusader/go,cloudflare/go,binarycrusader/go,derekmarcotte/go,Endika/go,CAFxX/go,kim-racktop/go,derekmarcotte/go,akutz/go,roth1002/go,binarycrusader/go,goodlang/good,binarycrusader/go,CAFxX/go,cyberroadie/go,derekmarcotte/go,josharian/go,mwhudson/go,polyverse-security/go,nawawi/go,suncycheng/go,Samurais/go,4ad/go,vanloswang/go,vsekhar/elastic-go