Introduce libfleet.sh and a new 'fleet' subcommand to ixll for managing
and operating enrolled Infix devices via RESTCONF.
Device configuration is stored in ~/.config/infix/config.json
(chmod 600): and organised by profile, allowing bulk operations across
groups of devices (e.g. all aarch64 targets).
New commands:
ixll fleet enroll [-d] [-p profile] [-u user] [-w password] <name> <address>
ixll fleet list
ixll fleet upgrade <name|profile> <url>
ixll fleet backup [-o dir] <name|profile>
ixll fleet reboot <name|profile>
Upgrade runs in parallel across a fleet and shows a live per-device
progress bar by polling the infix-system:install-bundle RPC and the
installer state from the YANG operational data store.
The global -A flag (admin/admin) is honoured as a credential fallback
for devices enrolled without an explicit password.
Also fix a pre-existing typo: ">2" → ">&2" in the error path.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
