refactor: convert JNLP agents to sidecars

Rather than try to derive these agents from the CloudBees Core Agent
image, let's instead build up stand-alone images independent of the
current CloudBees version, so we can reclaim a bit of control over the
shape of the image.

Change-Id: I33bd79768b9f73eb79df39ca9594445d3853a2ac
Signed-off-by: Chris Kay <chris.kay@arm.com>
2 files changed