Don't bind Lucene Module in test unconditionally
Don't bind Lucene Module in test unconditionally

I805222 changed the binding to default back to Lucene for custom index
types. This breaks Google's internal test setup. If that change is
desired, we can adjust our internal setup, but that will take O(days).

This commit reverts only this chunk back to the prior state.

Change-Id: I119f073595597d467e418329d81e972bd9ebe3ab

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