systemd: handle new capabilities gracefully

Do not propogate error code if a capability is not known to systemd
and present it as a number.

BUG=b/182952897
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I8d40e94600a22f16979d897af4ca8a1b39b288e5
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/14430
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Roy Yang <royyang@google.com>
3 files changed