SVCPLAN-2704 Use custom fact to only enable DCGM on nodes with NVIDIA GPUs

[bsper2]

Right now we enable DCGM install and telegraf collection by default, but ideally this should use a fact to only install this when a node has an NVIDIA GPU.

Once that fact is in place the README.md should be updated to remove comments about turning the DCGM off on non nvidia gpu nodes

[billglick]

A couple of possible ways to tell if an NVIDIA GPU is installed in a given host:

# SEARCH PCI DEVICES - PROBABLY BETTER FOR A CUSTOM FACT
lspci | grep -i nvidia | egrep -iqw '3D|Tesla' && echo true || echo false

# RUN nvidia-smi - RELIES ON NVIDIA SOFTWARE TO BE INSTALLED
nvidia-smi | grep -q NVIDIA && echo true || echo false

[billglick]

I think the fact could be written something like the following:

Facter.add(:nvidia_gpu) do
  setcode do
    `lspci | grep -i nvidia | egrep -iqw '3D|Tesla' && echo true || echo false`.strip
  end
end

Eventually it may also be useful to list the type(s) of NVIDIA GPUs installed. But that is beyond this scope.