Fix rt curl ServerID environment variable usage

[agrasth]

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Fix: Ensure jfrog rt curl Uses JFROG_CLI_SERVER_ID When Set
Issue
Currently, jfrog rt curl does not respect the JFROG_CLI_SERVER_ID environment variable when no --server-id flag is provided. Instead, it always defaults to the server configured via jfrog c add. This PR addresses issue #2870.

Changes Made

• Updated curlCmd in artifactory/cli.go to check for JFROG_CLI_SERVER_ID when --server-id is not explicitly set.
• Modified test cases in artifactory_test.go to validate the new behavior.
• Introduced structured test runs to ensure:
  • Default server config is used when no server-id or env var is set.
  • --server-id flag takes precedence over JFROG_CLI_SERVER_ID.
  • JFROG_CLI_SERVER_ID takes precedence over the default configuration.

Impact

• Ensures consistency with environment variable behavior.
• Provides better flexibility for users relying onJFROG_CLI_SERVER_ID.

Testing

• Added multiple test cases covering different priority scenarios.
• Verified jfrog rt curl behavior using structured test runs.

[github-actions]

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[agrasth]

I have read the CLA Document and I hereby sign the CLA

[github-actions]

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