Problem: node can't quit by signal

[yihuang]

Solution:

• cleanup graceful shutdown procedure

Closes: #XXX

Description

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 33 lines in your changes missing coverage. Please review.

Project coverage is 46.60%. Comparing base (a2ad87c) to head (139eb3e).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
server/json_rpc.go	0.00%	17 Missing ⚠️
server/start.go	0.00%	13 Missing ⚠️
testutil/network/util.go	0.00%	2 Missing ⚠️
testutil/network/network.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #543      +/-   ##
===========================================
+ Coverage    46.55%   46.60%   +0.05%     
===========================================
  Files          181      181              
  Lines        14542    14526      -16     
===========================================
  Hits          6770     6770              
+ Misses        7052     7036      -16     
  Partials       720      720              

Files with missing lines	Coverage Δ
testutil/network/network.go	0.00% <0.00%> (ø)
testutil/network/util.go	0.00% <0.00%> (ø)
server/start.go	19.79% <0.00%> (+0.83%)	⬆️
server/json_rpc.go	0.00% <0.00%> (ø)