Avoid null pointer exception when comparing JDBC connections

Spring Boot extension for the transactional driver doesn't know database URL and uses provided XADataSource to create connection. However, ConnectionImpl expects URL, username and password to not be null https://github.com/jbosstm/narayana/blob/5.5.0.Final/ArjunaJTA/jdbc/classes/com/arjuna/ats/internal/jdbc/ConnectionManager.java#L91. As a result NullPointerException is thrown if connection is reused.