I hope this puts a lot of questions about SIM cards to rest. I found
that the warning also sometimes applies to "dead" SIM cards which have
expired a long time ago.
Run `busybox ip route` to determine whether the device has an active SIM
card. That command has been manually tested on Moxee, Orbic and TP-Link.
It's prefixed with `busybox` because that makes it more likely it would
work on UZ801, though it wasn't tested there. If the command invocation
fails, the alert is suppressed and a warning is logged.
The command is only run once on pageload. It could've been part of the
status endpoint, but then the UI would poll it way too often.
