e2e: special case "Unexpected EOF" errors
e2e: special case "Unexpected EOF" errors

This is an attempt at deflaking the e2e exec tests, and a way to improve
messages.

e2e occasionally fail with "unexpected EOF" even though the exec output matches
expectations. I suspect there is a race in handling EOF in server/http handling.

Here, we special case this error and ensures we get all failures,
to help debug the case better.

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