Ensure KUKSA.val JWT certificate gets installed

Ensure KUKSA.val JWT certificate gets installed

Recent changes accidentally resulted in the jwt.key.pub certificate
file for KUKSA.val server / databroker authorization not getting
installed, breaking databroker start up.  Explicitly install it from
our kuksa-certificates-server-agl package, and tweak the kuksa-val
recipe to package it in its kuksa-certificates-server package.

Bug-AGL: SPEC-4985

Change-Id: I94703da876718524da753b6b882b331b7f088431
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29469
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-boot-test: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account