So, when you are changing port on Ubuntu, there must already be some application using port 80 (most probably a web server like apache httpd) which is why your config is not working. If you want to mask 8080 redirect your requests through some web server (may be the one already added on your Ubantu machine).
For masking /tutor to just / there are 2 ways. One, you either put the contents of tutor.war in the ROOT folder of tomcat. Second, make an entry of "/tutor.index.html" in the welcome file list of web.xml present at <%tomcat_home%>/conf.
Take a close look on tomcat directory, you will get a clear picture of what you can do :)