Environment testing tasks not reporting errors correctly

[blakeneyops]

The following is detecting errors during execution, but not reporting them properly.

https://github.com/unifio/covalence/blob/master/lib/covalence/rake/rspec/envs_spec.rb

The problem is that

expect(TerraformCli.terraform_plan(path, args: args)).to be true

should be

expect { TerraformCli.terraform_plan(path, args: args) }.to_not raise_error

This class was also not properly updated for changes made in the v0.6+

[yuhunglin]

or just have both.