tomcat and unpackWar issue

[opencms]

http://www.opencms.org/en/index.html

My Plesk version is 8.2.1
on Linux box.

I tried to deploy the above application inside Plesk control panel. (use Tomcat)

Deploy is successfully.

However, the war file (opencms.war) is not unpack.
I want it to be unpack so I try to modify the server.xml

under my virtual host domain section,
modify the unpackWars from false to true.

restart tomcat

but it seems that the value will return back to "false" again.

Is Plesk will modify this value by itself?

I need to set unpackWars = true in order to run the OpenCms.