Apollo Client 3.7.0 context issue

apollographql/apollo-client#10166

1. run yarn test and see it fails.
2. change apollo client version to 3.6.10 in pacakge.json, and run yarn test. (it succeeds)

observe console logs.

with 3.7.0,

  console.log
    headerForwardLink#user-agent undefined

      at log (src/client.js:14:15)

  console.log
    headerForwardLink#cookie undefined

      at log (src/client.js:18:15)

with 3.6.10

  console.log
    headerForwardLink#user-agent user-agent-string

      at log (src/client.js:14:15)

  console.log
    headerForwardLink#cookie cookie-value

      at log (src/client.js:18:15)