With cellular modem but no sim card, many copies of pppd are running

[jchonig]

Terry says:

1e-37 (port 20218) has a modem with no sim card, and everything up to date. I just found it with a load factor of 127 and a zillion pppd processes running.
[11:31](https://ttn-ithaca.slack.com/archives/D1S3N7BUY/p1739338288833489)
So that bug is still present, at least on that device.
11:32
The Ansible stuff was all up to date and I did a full make apply. But I did tell it that it was a cellular gateway.
[11:32](https://ttn-ithaca.slack.com/archives/D1S3N7BUY/p1739338328975639)
I'm sure the problem will resurface if we let it sit for another 24 hours. I did a killall pppd just now, which got it back to normal. It was loaded enough that the basic station stuff was disconnecting.
11:33
and loaded enough that it was hard to connect to.

The fix in #88 does not seem to help this, so maybe it is not monit that is starting all the processes.

This can hopefully be reproduced by configuring use_cellular on a gateway with a cellular modem and no SIM card.

[terrillmoore]

The idea that it might be monit makes sense -- the problem doesn't manifest immediately, but only after some period of operation. It might be a monit periodic task that triggers this.