Previously, if the remote TFC/TFE instance doesn't happen to have a tool_version
record whose name exactly matches the value of `tfversion.String()`, Terraform
would be completely blocked from using the `terraform workspace new` command
(when configured with the tags strategy) — the API would give a 422 to the
whole create request.

This commit changes the StateMgr() function to do the work in two passes; first
create the workspace (which should work fine regardless), THEN update the
Terraform version and print a warning to the terminal if it fails (which 99% of
the time is a benign failure with little impact on your future CLI usage).