Tomcat Parallel Deployment, automatically undeploy old applications
You can configure Tomcat to remove the old applications. You need to add the undeployOldVersions attribute to the Host element and set it to true. You'll need to modify your host in server.xml to something like the following:
<Host undeployOldVersions="true" ...>
...
</Host>
See the Host documentation for details. In particular, this only works when automatic deployment is enabled.