cmd/go: for go get -insecure, skip TLS certificate checking
cmd/go: for go get -insecure, skip TLS certificate checking

The flag is already named -insecure. Make it more so.

If we're willing to accept HTTP, it's not much worse to accept
HTTPS man-in-the-middle attacks too. This allows servers
with self-signed certificates to work.

Fixes #13197.

Change-Id: Ia5491410bc886da0a26ef3bce4bf7d732f5e19e4
Reviewed-on: https://go-review.googlesource.com/18324
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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