Ignore failures when closing war files in tests

Update WarPackagingTests to ignore any IOExceptions when closing
created war files. Exceptions were sometimes thrown when running on a
Linux NTFS mount.

Fixes gh-3255

spring-boot-integration-tests/spring-boot-gradle-tests/src/test/java/org/springframework/boot/gradle/WarPackagingTests.java

@@ -99,6 +99,13 @@ public class WarPackagingTests {
 		checkWebInfLibProvidedEntries(war, expectedLibProvidedEntries);
 
 		checkWebInfLibEntries(war, expectedLibProvidedEntries);
+
+		try {
+			war.close();
+		}
+		catch (IOException ex) {
+			// Ignore
+		}
 	}
 
 	private void checkWebInfLibProvidedEntries(JarFile war, Set<String> expectedEntries)