Environment variable not available in action name

```sh
$ cat manifest.yaml
packages:
default:
actions:
${ACTION_NAME}:
function: index.js
runtime: nodejs
triggers:
${TRIGGER_NAME}:
feed: /whisk.system/alarms/alarm
rules:
${RULE_NAME}:
action: ${ACTION_NAME}
trigger: ${TRIGGER_NAME}

$ export ACTION_NAME=hello
$ export TRIGGER_NAME=alarm
$ export RULE_NAME=hello-alarm

$ wskdeploy --preview
Packages:
Name: default
bindings:
annotation:

* action: ${ACTION_NAME}
bindings:
annotation:

Triggers:
* trigger: alarm
bindings:
annotation:
- feed : /whisk.system/alarms/alarm

Rules
* rule: hello-alarm
annotation:
- trigger: alarm
- action: hello
```