release-24.1: sql/server: Fix license disable bug for single node clusters

[blathers-crl]

Backport 1/1 commits from #136926 on behalf of @spilchen.

/cc @cockroachdb/release

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License enforcement is intended to be disabled for single-node setups. However, when starting CockroachDB with start-single-node, license enforcement was only disabled on the initial startup. Subsequent restarts of the cluster did not correctly disable licensing. This fix addresses and resolves that issue.

This should be backported all the way back to 23.1.

Epic: None
Release note (bug fix): Fixed an issue where license enforcement was not consistently disabled for single-node clusters started with start-single-node, ensuring proper behavior on cluster restarts.

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Release justification: Important bug fix so that single node servers can run without license enforcement.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

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Also, please add a brief release justification to the body of your PR to justify this
backport.

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is