bugfix grpc ip direct connection status check

[kpango]

Description:

Related Issue:

Versions:

• Go Version: 1.21.5
• Docker Version: 20.10.8
• Kubernetes Version: v1.28.4
• NGT Version: 2.1.6

Checklist:

• I have read the CONTRIBUTING document and completed our CLA agreement.
• I have checked open Pull Requests for the similar feature or fixes?

Special notes for your reviewer:

[vdaas-ci]

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• 🙆‍♀️ /approve - approve
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• ✅ /gen-test - generate test codes
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• 🔚 2️⃣ 🔚 /label actions/e2e-deploy - run E2E deploy & integration test

[cloudflare-pages]

Deploying with    Cloudflare Pages

Latest commit:	29b6ff2
Status:	✅  Deploy successful!
Preview URL:	https://cba62ec5.vald.pages.dev
Branch Preview URL:	https://bugfix-internal-grpc-ip-conn.vald.pages.dev

View logs

[codecov]

Codecov Report

Attention: 19 lines in your changes are missing coverage. Please review.

Comparison is base (52ca812) 30.30% compared to head (29b6ff2) 30.31%.
Report is 4 commits behind head on main.

Files	Patch %	Lines
internal/net/grpc/pool/pool.go	0.00%	17 Missing ⚠️
hack/license/gen/main.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2316      +/-   ##
==========================================
+ Coverage   30.30%   30.31%   +0.01%     
==========================================
  Files         391      391              
  Lines       40945    40953       +8     
==========================================
+ Hits        12407    12415       +8     
- Misses      27875    27876       +1     
+ Partials      663      662       -1     

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[github-actions]

[FOSSA] The scan result will be available at https://app.fossa.com/projects/custom%2B21465%2Fvald/refs/branch/bugfix%2Finternal-grpc%2Fip-connection-idle-removal-problem/97c68eb9645d65a49ce0057f5a13adc1c6b710eb

[vdaas-ci]

Profile Report

type	vald-agent-ngt	vald-lb-gateway	vald-discoverer	vald-manager-index
cpu
heap

other images

[hlts2]

LGTM!!