The script afm-util wasn't reporting correctly
errors. The use of the output status of
afb-client-demo was possible but this solution
is simplest to output the error message.
Bug-AGL: SPEC-1863
Change-Id: I5ac919e615ed5c0f21589292e94a9c3d6209a83f Signed-off-by: José Bollo <jose.bollo@iot.bzh>