Three related fixes for running Monitor inside a container with
/:/host:ro bind-mounted and network_mode: host.
* config: when HF_MONITER_ROOTFS is set, read the default identifier
from <rootFS>/etc/hostname instead of os.Hostname(). Under
network_mode: host the UTS namespace is not shared, so os.Hostname()
returns a random docker-assigned string that changes across
recreations, causing the backend to treat each restart as a new
server.
* telemetry: log gopsutil errors from BuildPayload instead of silently
swallowing them. Previously a missing /host mount would send a
payload full of zeroed fields with no indication of failure.
* docker-compose: drop the 'ports:' block. It is silently ignored
under network_mode: host (the bridge server binds directly on the
host's 127.0.0.1:MONITOR_PORT).