Log roles.yml changes in TokenAuthIntegTests

This test recently failed and it appears that the cause was that
roles.yml was deleted while the cluster was still running.
This turns on logging for the FileRolesStore so that changes to file
based roles can traced more easily.

Original commit: elastic/x-pack-elasticsearch@fbce5a8

Author: tvernum

plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/TokenAuthIntegTests.java

@@ -46,6 +46,7 @@
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoTimeout;
 import static org.hamcrest.Matchers.equalTo;
 
+@TestLogging("org.elasticsearch.xpack.security.authz.store.FileRolesStore:DEBUG")
 public class TokenAuthIntegTests extends SecurityIntegTestCase {
 
     @Override