Add FEATURE_GATES env to controller deployment template

[michaelhtm]

Description of changes:
This change will allow us to include environment variable
for feature gates, specifically when testing specific ones

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[michaelhtm]

/retest

[a-hilaly]

/lgtm

[ack-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: a-hilaly, michaelhtm

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[michaelhtm]

/retest

[michaelhtm]

/retest

[michaelhtm]

/retest

[michaelhtm]

/retest

[ack-prow]

@michaelhtm: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
verify-attribution	eaa5341	link	false	/test verify-attribution

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