Fixes #2518 - @connection breaks MockedProvider

[ajmath]

When trying to mock a query that uses the @connection directive, the mock would never be triggered due to an inconsistent key in MockLink. This PR adds a method to normalize the incoming mock so that the request made by the apollo client matches the one in MockLink.

See #2518 for more details

Checklist:

• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• If this was a change that affects the external API used in GitHunt-React, update GitHunt-React and post a link to the PR in the discussion.

[hwillson]

Thanks for this @ajmath!