Multiple simultaneous requests result in HTTP 304

[worldomonation]

Certain test suites in the Playwright E2E project intermittently encounter HTTP 304 status when first attempting to load a calypso URL.

The failure is presumably occurring here when the <baseCalypsoURL>/log-in endpoint is being hit by multiple containers at the same time. Retrying (automatically via magellan) usually results in the next iteration being able to access the endpoint as normal.

Slack thread: p1624428683011700-slack-C01BVMH5C20