INT-3416 Reset SMS.copyOnGet By Default

JIRA: https://jira.spring.io/browse/INT-3416

Fix the `SimpleMessageStoreTests`

spring-integration-core/src/test/java/org/springframework/integration/store/SimpleMessageStoreTests.java

@@ -110,6 +110,7 @@ public class SimpleMessageStoreTests {
 	@Test
 	public void shouldCopyMessageGroup() throws Exception {
 		SimpleMessageStore store = new SimpleMessageStore();
+		store.setCopyOnGet(true);
 		Message<String> testMessage1 = MessageBuilder.withPayload("foo").build();
 		store.addMessageToGroup("bar", testMessage1);
 		assertNotSame(store.getMessageGroup("bar"), store.getMessageGroup("bar"));