Updated docs and testcase for ParallelScan

Small documentation clarification and testcase update JAVA-1105

Author: rozza

src/main/com/mongodb/ParallelScanOptions.java

@@ -35,12 +35,16 @@ public static class Builder {
 
         /**
          * Set the requested number of cursors to iterate in parallel.
+         * <p>
+         *     Note: this is the maximum number of cursors the server will return, it may return fewer cursors.
+         * </p>
          *
-         * @param numCursors the number of cursors requested, which must be >= 1
+         * @param numCursors the number of cursors requested, which must be >= 1 and <= 10000
          * @return this
          */
         public Builder numCursors(final int numCursors) {
             isTrue("numCursors >= 1", numCursors >= 1);
+            isTrue("numCursors <= 10000", numCursors <= 10000);
 
             this.numCursors = numCursors;
             return this;

src/test/com/mongodb/DBCollectionTest.java

@@ -550,8 +550,9 @@ public void testParallelScan() throws UnknownHostException {
             collection.insert(new BasicDBObject("_id", i));
         }
 
-        List<Cursor> cursors = collection.parallelScan(ParallelScanOptions.builder().numCursors(3).batchSize(1000).build());
-        assertEquals(3, cursors.size());
+        int numCursors = 10;
+        List<Cursor> cursors = collection.parallelScan(ParallelScanOptions.builder().numCursors(numCursors).batchSize(1000).build());
+        assertTrue(cursors.size() <= numCursors);
 
         for (Cursor cursor : cursors) {
             while (cursor.hasNext()) {