Make IntegrationTestPropertiesListener public

Make IntegrationTestPropertiesListener public so that it can be used
when @TestExecutionListeners are declared on a parent class.

See gh-2135

Author: philwebb

spring-boot/src/main/java/org/springframework/boot/test/IntegrationTestPropertiesListener.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.test;
 
+import org.springframework.core.Ordered;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.test.context.MergedContextConfiguration;
@@ -30,7 +31,7 @@
  * @author Phillip Webb
  * @since 1.2.0
  */
-class IntegrationTestPropertiesListener extends AbstractTestExecutionListener {
+public class IntegrationTestPropertiesListener extends AbstractTestExecutionListener {
 
 	@Override
 	public void prepareTestInstance(TestContext testContext) throws Exception {
@@ -57,4 +58,9 @@ private void addPropertySourceProperties(TestContext testContext, String[] prope
 		}
 	}
 
+	@Override
+	public int getOrder() {
+		return Ordered.HIGHEST_PRECEDENCE;
+	}
+
 }