Fix Maps.newHashMapWithExpectedSize for JDK8.

Two changes to HashMap in JDK8 have affected this test:
- First, the table field is set lazily, so it is null until you add
elements to the Map.
- Second, the resize() calculations have changed in JDK8, so we adjust
the predicted size accordingly.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=72650895