Use orElseGet to delay call until necessary (#1210)

src/main/java/com/zaxxer/hikari/pool/HikariPool.java

@@ -621,7 +621,7 @@ public final class HikariPool extends PoolBase implements HikariPoolMXBean, IBag
    private ScheduledExecutorService initializeHouseKeepingExecutorService()
    {
       if (config.getScheduledExecutor() == null) {
-         final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElse(new DefaultThreadFactory(poolName + " housekeeper", true));
+         final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElseGet(() -> new DefaultThreadFactory(poolName + " housekeeper", true));
          final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
          executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
          executor.setRemoveOnCancelPolicy(true);