Share Env attributes with cfgOptions.

In #1823, functionality was added to check module dependencies during
destroy operations. This included creating a fresh `TerragruntOptions`
object [1] which, by default, has an empty map for the `Env` attribute [2].
This means we're losing all environment variables when checking for
dependencies.

[1] https://github.com/gruntwork-io/terragrunt/pull/1823/files#diff-2ce1e65bb8a23011007dae779c8bacbc45d28560b1bc4e7dc1079f52fd22cf14R504
[2] https://github.com/gruntwork-io/terragrunt/blob/7788a525ab61641211e3f8a127ed53b450e96bc8/options/options.go#L256

configstack/module.go

@@ -590,6 +590,7 @@ func FindWhereWorkingDirIsIncluded(terragruntOptions *options.TerragruntOptions,
 			terragruntOptions.Logger.Debugf("Failed to build terragrunt options from %s %v", dir, err)
 			return nil
 		}
+		cfgOptions.Env = terragruntOptions.Env
 		cfgOptions.LogLevel = terragruntOptions.LogLevel
 		if terragruntOptions.TerraformCommand == "destroy" {
 			var hook = NewForceLogLevelHook(logrus.DebugLevel)