[stable/ambassador] AMBASSADOR_ID not set on ambassador-pro containers

[bloxgate]

Describe the bug
When using Ambassador Pro and a non-default AMBASSADOR_ID, the environment variable needs to be set on both containers, as stated here. However, AMBASSADOR_ID is only set on the ambassador container.

Version of Helm and Kubernetes:
Helm: v2.13.1
Kubernetes: 1.10.11

Which chart:
stable/ambassador v2.8.2

What happened:
A pod containing ambassador and ambassador-pro containers was created. The AMBASSADOR_ID environment variable was only set on the ambassador container.

What you expected to happen:
The AMBASSADOR_ID variable is set on both the ambassador and ambassador-pro containers.

How to reproduce it (as minimally and precisely as possible):
Install the helm chart with the following values:

daemonSet: true

env:
  AMBASSADOR_ID: "ambassador-staging"

pro:
  enabled: true
  licenseKey:
    value: [license key here]

Anything else we need to know:

[Bekt]

/cc @kflynn @lydiverny

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Any further update will cause the issue/pull request to no longer be considered stale. Thank you for your contributions.