FullTextIndexingTest needs very long (60 seconds) timeout for Oak

I had to increase the timeout to 60 seconds in the launchpad/integration-tests/.../FullTextIndexingTest to make it pass reliably with Oak on Jenkins.

I suspect the Oak indexes are not always ready when the test runs: the error log shows "org.apache.jackrabbit.oak.plugins.index.IndexUpdate Indexing report" messages after the test runs, which I suppose signals the end of an indexing task.

We should find out how to take this into account in the tests, either wait for all required indexes to be ready before starting our tests, or having a way to find out whether a specific set of indexes is ready before starting a specific test.