Properly handle empty pages in MultiPageResultSet

If there are multiple empty pages consecutively, the old
logic did not handle the situation correctly. Use a while
loop to move past many possible empty pages.

(cherry picked from commit 40da47a)

core/src/main/java/com/datastax/oss/driver/internal/core/cql/MultiPageResultSet.java

@@ -93,7 +93,7 @@ protected Row computeNext() {
     }
 
     private void maybeMoveToNextPage() {
-      if (!currentRows.hasNext() && currentPage.hasMorePages()) {
+      while (!currentRows.hasNext() && currentPage.hasMorePages()) {
         BlockingOperation.checkNotDriverThread();
         AsyncResultSet nextPage =
             CompletableFutures.getUninterruptibly(currentPage.fetchNextPage());