Refactor EbeanServerFactory internals - use SpiContainerShutdown interface for container shutdown mechanism

src/main/java/io/ebeaninternal/server/lib/DContainerShutdown.java

@@ -0,0 +1,14 @@
+package io.ebeaninternal.server.lib;
+
+import io.ebean.service.SpiContainerShutdown;
+
+/**
+ * Default container shutdown implementation.
+ */
+public class DContainerShutdown implements SpiContainerShutdown {
+
+  @Override
+  public void shutdown() {
+    ShutdownManager.shutdown();
+  }
+}