Host Upgrade addon should support RHEL

[Kerwood]

Please add support for RHEL in the Host Upgrade addon.
I'm guessing its no different from supporting CentOS?

2019/12/18 10:25:02 pharos-host-upgrades version 0.3.1 (Go go1.10.2)
2019/12/18 10:25:02 Load config from --config-path=/etc/host-upgrades
2019/12/18 10:25:02 Copying configs to --host-mount=/run/host-upgrades
2019/12/18 10:25:02 hosts/ubuntu probe mismatch: Red Hat Enterprise Linux Server 7.7 (Maipo)
2019/12/18 10:25:02 hosts/centos probe mismatch: Red Hat Enterprise Linux Server 7.7 (Maipo)
2019/12/18 10:25:02 hosts/debian probe mismatch: Red Hat Enterprise Linux Server 7.7 (Maipo)
2019/12/18 10:25:02 Failed to probe host: No hosts matched