Fix for proxy exiting early during start-up

[alexellis]

Description

Fix for proxy exiting early during start-up

Motivation and Context

When a proxied core service was accessed before it was ready to accept a connection, due to a start-up, restart, etc of a core service, then the proxy exited instead of continuing to accept new connections.

This meant having to restart faasd and hope the race condition worked itself out, or that no incoming requests were made.

Tested with Grafana, which seemed to manifest the issue the most.

Jan 30 08:58:09 derek faasd[1684930]: 2025/01/30 08:58:09 Proxy from: 127.0.0.1:8080, to: gateway:8080 (10.62.1.184)
Jan 30 08:58:09 derek faasd[1684930]: 2025/01/30 08:58:09 Proxy from: 127.0.0.1:8083, to: dashboard:8083 (10.62.1.185)
Jan 30 08:58:09 derek faasd[1684930]: 2025/01/30 08:58:09 Proxy from: 10.62.0.1:5432, to: postgresql:5432 (10.62.1.187)
Jan 30 08:58:09 derek faasd[1684930]: 2025/01/30 08:58:09 Proxy from: 127.0.0.1:9090, to: prometheus:9090 (10.62.1.183)
Jan 30 08:58:09 derek faasd[1684930]: 2025/01/30 08:58:09 Proxy from: 127.0.0.1:3000, to: grafana:3000 (10.62.1.189)
Jan 30 08:58:10 derek faasd[1684930]: 2025/01/30 08:58:10 Unable to dial: 10.62.1.189:3000, error: dial tcp 10.62.1.189:3000: connect: connection refused

How Has This Been Tested?

After the fix, the warning is still logged, but the proxy continues to accept new connections.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)