Disable unexpected datasource initialization

This commit restore the disabling of datasource initialization that was
accidently removed in db33a754 so that other tests aren't affected by it.

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/transaction/TransactionAutoConfigurationTests.java

@@ -69,7 +69,8 @@ public class TransactionAutoConfigurationTests {
 	@Test
 	public void singleTransactionManager() {
 		load(new Class<?>[] { DataSourceAutoConfiguration.class,
-				DataSourceTransactionManagerAutoConfiguration.class });
+				DataSourceTransactionManagerAutoConfiguration.class },
+				"spring.datasource.initialize:false");
 		PlatformTransactionManager transactionManager = this.context
 				.getBean(PlatformTransactionManager.class);
 		TransactionTemplate transactionTemplate = this.context