Make Bigtop-Mpack compatible with Ubuntu 20.04

There is no compatibility for Ubuntu 20.04 to deploy Bigtop over Ambari. There is no choose option in Ambari to add a repo for this os version and I could not find the position to add the os family. If I add a repo in the repo.xml I get a failure when I try to deploy because the repo for a os-family is still not compatible with the system. If I change the os-family in the repo file the whole stack disappear in Ambari.

Also the os_family.json lacks the option for ubuntu20 what leads to a failure on registering hosts.