fix: prevent redis shutdown

[vk-rv]

We found that redis shutdown is unexpected on grpc server exit while redeploying Flipt.

[markphelps]

Great find. Thank you!

[markphelps]

@all-contributors please add @vk-rv for code

[allcontributors]

@markphelps

I've put up a pull request to add @vk-rv! 🎉

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 72.35%. Comparing base (f997fb9) to head (dbcfdb3).
Report is 363 commits behind head on main.

Files	Patch %	Lines
internal/cmd/grpc.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3111      +/-   ##
==========================================
+ Coverage   70.78%   72.35%   +1.57%     
==========================================
  Files          91      102      +11     
  Lines        8729     7662    -1067     
==========================================
- Hits         6179     5544     -635     
+ Misses       2165     1708     -457     
- Partials      385      410      +25     

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