[keyserver] Run webapp through comm services cluster

Summary:
Run webapp on the comm services cluster. Will not land until web.comm.app has been properly set up on prod

This will require a new keyserver image push with https://phab.comm.dev/D12927

Depends on D12906

Test Plan:
terraform apply. Switched comm.software to point to web app load balancer and accessed the working web app.

Used wyilio/keysever:1.0 for testing

Reviewers: bartek, varun

Reviewed By: bartek, varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12928