The --insecure option on the included clients is not working

[vatine]

Just a bit of a preface why we want/need the --insecure option, so it's clear why this is necessary. We need to run mosquitto in a Kubernetes container and we have, as a policy, that all containers should have a liveness check. For hat purpose, we're using the "exec" type of liveness check and run mosquitto_sub to connect to "mqtts://127.0.0.1:2283/liveness_probe_subject" (we will not know the IP of the pod when we write the manifest and we do not want to check more than "Mosquitto responds").

The last version we know this worked on was 2.0.14 (it may have worked on later versions, I have not done the bisecting) and from some experimentation, where it seems to break somewhere in the "pre-verification" (the test setup uses a self-signed cert and CA, both expiring in 2027).

I have managed to get this to work in two ways, one is to move the preverify_ok check to after the code pulls the struct mosquitto *mosq out of the SSL context, then instead of returning 0, return mosq->tls_insecure.

The other is to remove the preverify_ok check and return 1 after the check (after all, insecure means "insecure", right?).

I am actually not sure if this has started failing due to a change in OpenSSL, or due to a change in the mosquitto codebase.