/etc/tomcat8/Catalina/localhost/guacamole.xml is in guacamole 0.9.9+dfsg-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/tomcat8/Catalina/localhost/../../../guacamole/tomcat.xml
/etc/tomcat8/Catalina/localhost/../../../guacamole/tomcat.xml