e2e: ensure repositories are cloned not just added
Created by: unknwon
We do not wait and request the page right after adding the external service. It is one of sources why these tests are flaky because very often they would only see "clone in progress" instead of the actual blob content if the e2e code executes too fast (before gitserver could finish cloning).
Part of https://github.com/sourcegraph/sourcegraph/issues/10709.