Debian package force removing /etc/tomcat*/Catalina/localhost/xwiki.xml file in postrm

This makes XWiki not registered in tomcat anymore when upgrading from 5.0 to 5.0.1

This rm used to be needed when symlinks were not supported but since 5.0 we have proper symlinks in the generated deb package which make all the rm in the various postrm scripts worst than useless since they disturb the upgrade process.

The workaround is to recreated the link to /etc/xwiki/xwiki-tomcat.xml as /etc/tomcat7/Catalina/localhost/xwiki.xml (for tomcat7, change the number for other versions of tomcat).