Maven indexer related tests fail on CI

[AObuchow]

Tests related to the maven indexer (eg. testVersionCompletion()) fail on CI builds.
Currently, if testVersionCompletion runs with no timeout set, it will eventually cause the entire build to timeout.
I've been trying to get them to pass, with no luck so far.

Some potential solutions to explore:

1. Download the index from a smaller repository. This will reduce the chance of timing out during the index download. However, the maven central repository is currently set as a default remote repository in MavenRepositoryCache - this would have to be removed or temporarily disabled for the test.
2. Make a seperate test which ensures that the index has been completely downloaded before running other tests. Ideally, if this test fails, other maven indexer related tests should be skipped.