Underflow in connected_clients metrics

[kishorviswanathan]

Describe the bug
We have issues with the dragonfly_connected_clients under flowing and becoming a very huge value.

#5914 has the details and workaround.

To Reproduce
Not sure how to reproduce.

Expected behavior
The connected_clients metric shouldn't underflow

Screenshots

Environment (please complete the following information):

• OS: Container Optimized OS
• Kernel: Linux hostname 6.6.87+ #1 SMP Sat Jun 14 10:09:14 UTC 2025 x86_64 AMD EPYC 7B13 AuthenticAMD GNU/Linux
• Containerized?: Docker Compose
• Dragonfly Version: 1.31.2

Additional context
This doesn't happen when connection migration is disabled. ie --migrate_connections=false