provider/template: Fix panic in cloudinit config

[grubernaut]

Fixes an uncaught panic during an interface cast in the template_cloudinit_config data source.

Fixes: #13572

$ make test TEST=./builtin/providers/template TESTARGS="-v -run=TestRender_handlePanic"
==> Checking that code complies with gofmt requirements...
==> Checking AWS provider for unchecked errors...
==> NOTE: at this time we only look for uncheck errors in the AWS package
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/12 10:46:33 Generated command/internal_plugin_list.go
go test -i ./builtin/providers/template || exit 1
echo ./builtin/providers/template | \
                xargs -t -n4 go test -v -run=TestRender_handlePanic -timeout=60s -parallel=4
go test -v -run=TestRender_handlePanic -timeout=60s -parallel=4 ./builtin/providers/template
=== RUN   TestRender_handlePanic
--- PASS: TestRender_handlePanic (0.00s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/template       0.028s

[apparentlymart]

Looks like a good quick fix! Error is definitely better than crash. 😀

[catsby]

👍

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.