https://issues.apache.org/jira/browse/AMQ-4705 - ensure cached lastModified is externally visible - hardened test showed window for missed mod

activemq-broker/src/main/java/org/apache/activemq/util/LockFile.java

@@ -83,6 +83,7 @@ public class LockFile {
                 }
                 if (lock != null) {
                     //Set lastModified only if we are able to successfully obtain the lock.
+                    readFile.getChannel().force(true);
                     lastModified = file.lastModified();
                     lockCounter++;
                     System.setProperty(getVmLockKey(), new Date().toString());