/usr/lib/x86_64-linux-gnu/libavahi-client.so is in libavahi-client-dev 0.7-3.1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libavahi-client.so.3.2.9
/usr/lib/x86_64-linux-gnu/libavahi-client.so.3.2.9