add terraform enterprise backend skip_cert_verification option

[ryancbutler]

The Terraform enterprise backend doesn't seem to have any ability to ignore cert verification like the HTTP backend. This requires each machine to have the certificate chain installed wherever terraform is run causing additional steps in management and deployment.

[pkolyvas]

Thanks for the feedback @ryancbutler . I've forwarded your request to the Terraform Enterprise & Cloud teams.

[pkolyvas]

Re-opened - backend.

[dipesharora]

It would be nice to have an option to skip cert validation. Just ran into the same issue.