Update index tests

Always use latest index schema version; if we need to add tests of
older versions (e.g. ensuring the schema version for the last Gerrit
release still works), we should add those manually.

Remove AbstractIndexQueryChangesTest and move all its tests to the
base class, since we have no non-index implementation.

Change-Id: I5d4af1034155a004e31d782c74dc56677756ab8d
4 files changed