nginx: Added ACME redirect to main domain based on alias domain fix

This allows sites using redirect=proxy to still generate ACME
certificates by not passing the acme requests through to the proxy.

We should also consider using this for other features available such as
own error documents, SSI and custom directives.
1 job for !1604 with 4618-allow-acme-with-proxy-redirect in 7 minutes and 27 seconds (queued for 3 seconds)
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