Trojan and SSL rekey timers counting backwards
I'm using the GlobalProtect protocol in order to connect to the VPN. I tried using the `--force-trojan=3600` argument in order to force sending the HIP report every hour, but the HIP report was not being sent. Upon sending SIGUSR1 to the OpenConnect process I noticed that a value larger than 3600 was listed for the next invocation; sending the signal again showed that the value had **increased** since the last signal. The timer appears to be counting backwards, so the report is never sent! Below is an example of the behavior:
```
[2023-11-20 18:27:45] Configured as REDACTED, with SSL connected and ESP established
[2023-11-20 18:27:45] Session authentication will expire at Tue Nov 21 09:26:45 2023
[2023-11-20 18:27:45] RX: 31893 packets (36754577 B); TX: 19568 packets (3780802 B)
[2023-11-20 18:27:45] SSL ciphersuite: (TLS1.2)-(ECDHE-SECP256R1)-(RSA-SHA256)-(AES-256-GCM)
[2023-11-20 18:27:45] Next SSL rekey in 25200 seconds
[2023-11-20 18:27:45] Next Trojan invocation in 3660 seconds
[2023-11-20 18:27:52] Configured as REDACTED, with SSL connected and ESP established
[2023-11-20 18:27:52] Session authentication will expire at Tue Nov 21 09:26:45 2023
[2023-11-20 18:27:52] RX: 31895 packets (36754799 B); TX: 19572 packets (3781069 B)
[2023-11-20 18:27:52] SSL ciphersuite: (TLS1.2)-(ECDHE-SECP256R1)-(RSA-SHA256)-(AES-256-GCM)
[2023-11-20 18:27:52] Next SSL rekey in 25207 seconds
[2023-11-20 18:27:52] Next Trojan invocation in 3667 seconds
```
Out of curiosity I tried using `--force-trojan=-3600` but that appeared to DoS the VPN server. I'm primarily experiencing this on Ubuntu 22.04 which has OpenConnect v8.20-1 but reproduced the issue on the latest commit (a6a2f18b72bc9708330007b474b63ae0850c1623) as well.
issue