[debian] replaced apt-key with more modern approach

[cjac]

As requested in GoogleCloudPlatform/ops-agent#1132

Thank you @sbconslt for hounding us to get it done.

[cjac]

Come to think of it, I prefer --no-default-keyring --keyring to --dearmor -o since the former can store multiple keys in the file.

[braydonk]

Since this is just a copy of this script and not the canonical version, I would suggest closing this PR; the correct approach would be to change the actual script and copy it into this repo again.

[cjac]

@braydonk - oh? This is not the original? Can you tell me where the original lives? I do want to update the file at https://dl.google.com/cloudagents/add-google-cloud-ops-agent-repo.sh and I thought this was what fed that one.

Can you please advise? What file should be modified?

[braydonk]

@cjac I have sent you a message internally with the source location of the script that is launched to that URL.

[iennae]

@braydonk can you share with me as well as I haven't heard that there is a source