Switches the rolling upgrade tests from upgrading two nodes to upgrading
three nodes which is much more realistic and much better able to find
unexpected bugs. It upgrades the nodes one at a time and runs tests
between each upgrade. As such this now has four test runs:
1. Old
2. One third upgraded
3. Two thirds upgraded
4. Upgraded
It sets system properties so the tests can figure out which stage they
are in. It reuses the same yml tests for the "one third" and "two
thirds" cases because they are *almost* the same case.
This rewrites the yml-based indexing tests to be Java based because the
yml-based tests can't handle different expected values for the counts.
And the indexing tests need that when they are run twice.
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