build failures retreiving key

[tpdownes]

We see build errors when retrieving apt keys every so often. e.g.

Build failed: The command '/bin/sh -c apt-key adv --keyserver pgp.mit.edu --recv-key 8325FECB83821E31D3582A69CE050D236DB6FA3F' returned a non-zero code: 2

I suspect problem is that docker build environment has unreliable networking or the keyserver gets hit too hard by the docker build environment (these images build when debian/centos images get updated so it might be a time of peak keyserver activity).

I believe a safer approach would be one of the following:

1. Download the ASCII key, place it in repo, COPY into image and run apt-key.
2. Find a binary key, place it in repo and copy it into /etc/apt/trusted.gpg.d. Might copy/match the file from the "repo package" if one exists.

Either approach should be done by generating as few layers as possible.