Improve message for start trace behavior.

[YingChen1996]

Description

Please add an informative description that covers that changes made by the pull request and link all relevant issues.

All Promptflow Contribution checklist:

• The pull request does not introduce [breaking changes].
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.
• Create an issue and link to the pull request to get dedicated review from promptflow team. Learn more: suggested workflow.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[github-actions]

SDK CLI Global Config Test Result dev/chenyin/start_trace_message

3 tests   3 ✅  46s ⏱️
1 suites  0 💤
1 files    0 ❌

Results for commit 9daa840.

♻️ This comment has been updated with latest results.

[github-actions]

promptflow SDK CLI Azure E2E Test Result dev/chenyin/start_trace_message

  4 files    4 suites   5m 31s ⏱️
190 tests 170 ✅ 20 💤 0 ❌
760 runs  680 ✅ 80 💤 0 ❌

Results for commit 9daa840.

♻️ This comment has been updated with latest results.

[github-actions]

SDK CLI Test Result dev/chenyin/start_trace_message

   12 files     12 suites   48m 27s ⏱️
  496 tests   478 ✅ 18 💤 0 ❌
1 984 runs  1 912 ✅ 72 💤 0 ❌

Results for commit 9daa840.

♻️ This comment has been updated with latest results.