Allow Helm lookup in manifest experiment

[omgftw]

Description

This fix is for the "manifest" experiment.

Some charts (notably aws-load-balancer-controller) depend on Helm's lookup function to get data from certain resources. Often if they cannot get this data, they will generate new data (ex: a UUID). In this case, this will cause a permanent diff and you will not be able to upgrade the chart, since the plan will always change, resulting in a "Provider produced inconsistent final plan" error.

To resolve this, I set the "DryRunOption" to "server". According to Helm's docs:

Setting --dry-run==server will additionally execute any lookup in your chart towards the server.

Acceptance tests

• Have you added an acceptance test for the functionality being added?
  ^ No, but I have tested the change manually.

Release Note

Release note for CHANGELOG:

NONE

References

#805
#711

Community Note

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[hashicorp-cla]

All committers have signed the CLA.

[ThibaultSaillan]

i've test your change @omgftw and it worked like a charm ! I was blocked between render my local chart and the need of aws-load-balancer-controller chart ! Hope they'll integrate this sooon !

[sheneska]

Thanks for the changes @omgftw! 🚀
Could you add a changelog please so we can go ahead and get this merged?