misc: Add some link examples to sysctl.conf (catch up)

misc: Add some link examples to sysctl.conf (catch up)

--------------- Original Master Branch Commit Message:
Adds both examples to the sample sysctl.conf configuration file
to enable link protection for both hard and soft links.

Most kernels probably have this enabled anyhow.

References:
 https://bugs.debian.org/889098
 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-18078
 https://github.com/torvalds/linux/commit/561ec64ae67ef25cac8d72bb9c4bfc955edfd415

Signed-off-by: Jim Warner <james.warner@comcast.net>