Include the GPG key within the setup_meter.sh script itself.  See BOUNDARY-3808.

Summary: Place the Boundary GPG key in the setup_meter.sh script so that it's no longer a separate download/install.

Test Plan: Check the systems which use the GPG key still install the GPG key as expected.

Reviewers: busterb

CC: philip, schneider

Differential Revision: http://phabricator.cid1.boundary.com/D2748