remove the dependency to vaadin-spring from tests

[vlukashov]

When building the flow-server package I do not want any of the tests to depend on the vaadin-spring package, so that I can build and release flow-server without having to solve circular dependency issues.

Currently, the flow-ccdm-connect integration test for Flow has a dependency to vaadin-spring. vaadin-spring in its turn has a compile-time dependency to flow-server. That makes maintenance and release process difficult (and in many ways broken).

details: https://vaadin.slack.com/archives/CDNTYMS9H/p1574757699131200

DoD:

• the flow-ccdm-connect integration test is moved from the flow repo into the vaadin-spring repo and there is no circular dependency between flow and vaadin-spring.