/usr/share/doc/libqgis-server2.8.6/changelog.Debian.gz is in libqgis-server2.8.6 2.8.6+dfsg-1build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libqgis-server2.8.6/../libqgis-core2.8.6/changelog.Debian.gz