allow_partial_results_with_maxTimeMS.js getMores are too slow

As seen in BF-26772, the getMore command in allow_partial_results_with_maxTimeMS.js:191 is taking very long to execute, causing a timeout instead of returning the partial results we expect to see.  This is because the initial find uses a tiny batch size of 1.  The subsequent getMore sets a much larger batch size, but the cursor retains its original batch size of 1, requiring the router to make hundreds of getMore requests to the remotes.

This behavior is actually quite confusing and I'll create another ticket to consider changing it.  However, the quick solution to this js test failure is to use a larger batch size in the initial find.