fix client config don't take effect (backport #9211)

[mergify]

This is an automatic backport of pull request #9211 done by Mergify.
Cherry-pick of b4d1a5e has failed:

On branch mergify/bp/release/v0.42.x/pr-9211
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Changes to be committed:
	modified:   client/config/config.go
	modified:   client/keys/show.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   client/keys/add.go

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[lgtm-com]

This pull request introduces 4 alerts when merging 55e4fdc into 1327224 - view on LGTM.com

new alerts:

• 3 for Useless assignment to local variable
• 1 for Unreachable statement

[amaury1093]

tACK.

test:

simd config keyring-backend // shows "os"
simd keys list // shows "os" backend keys
simd config keyring-backend test
simd keys list // shows "test" backend keys
simd keys add abc
simd keys list // shows "test" backend keys, incl. "abc"