#3412 Use existing/parent transaction with fetch query on ToMany paths

Fix such that LoadManyRequest uses the parent requests transaction rather
than obtain a new read only transaction to perform the fetch query.

ebean-core/src/main/java/io/ebeaninternal/api/LoadManyRequest.java

@@ -94,6 +94,7 @@ public final class LoadManyRequest extends LoadRequest {
   public SpiQuery<?> createQuery(SpiEbeanServer server) {
     BeanPropertyAssocMany<?> many = many();
     SpiQuery<?> query = many.newQuery(server);
+    query.usingTransaction(transaction);
     String orderBy = many.lazyFetchOrderBy();
     if (orderBy != null) {
       query.orderBy(orderBy);