System must be smart enought do not allow user to specify same cache location for User and System.
If user decide to remove application from User it will be also removed from the System.

All platforms.
To reproduce:

- run JCP
- in General/Temporary Internet Files/Settings set your own cache location (/home/user/user_cache)
- in deployment.properties file configure same location for system cache
(deployment.system.cachedir=/home/user/user_cache), close JCP
- run javaws -import -system http://java.sun.com/products/javawebstart/apps/notepad.jnlp
- go to Java Application Cache Viewer, you can see Notepad under User and System
- remove Notepad from User, it will be also removed from System