/usr/share/tomcat6/lib/servlet-api.jar is in tomcat6-common 6.0.39-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/tomcat6/lib/../../java/servlet-api-2.5.jar
/usr/share/tomcat6/lib/../../java/servlet-api-2.5.jar