[BFLCM-I-384] Include uninstall fixlets for *nix systems

https://bigfix.ideas.hcl-software.com/ideas/BFLCM-I-384

We have uninstall fixlets in the BES Support site for Windows and macOS ("TROUBLESHOOTING: Uninstall BES Client" and "TROUBLESHOOTING: Uninstall BES Client Mac OS"), but none for *nix systems. These fixlets are helpful to remove the client from systems remotely.