OPENDJ-2553 Constrain VLV index range queries when evaluating searches without VLV controls

Limited VLVIndex.evaluateNonVLVRequest() to CURSOR_ENTRY_LIMIT maximum:
- size limit are already verified in SearchOperationBasis.returnEntry().
- lookthrough limit and page size are already verified by EntryContainer.searchIndexed() and searchNotIndexed().

VLVIndex.java:
In evaluateNonVLVRequest(), when the count is bigger than CURSOR_ENTRY_LIMIT abort by returning null.