Avoiding problems when jtreg ClassPathProviderImpl is called from RepositoryUpdater.

[lahodaj]

There's a number of hacks to support OpenJDK's test. In particular, those test fail to index reasonably, so under normal circumstances, they are not indexed. And, normally, sourcepath is filtered for non-indexed roots. So, there's a hack that "initializes" the query for the test directory, even if it is not indexed. But - this crashes if, this happens inside RepositoryUpdater task.

The proposal here is to avoid initializing the query when inside the RU task, and initialize later.

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[dbalek]

Looks fine.