conn, util: make opentracing work again (#50551)

[ti-chi-bot]

This is an automated cherry-pick of #50551

What problem does this PR solve?

Issue Number: close #50508

Problem Summary: Caused by #40825, miss root span for opentracing tools.

What changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Start a TiDB cluster as opentracing.enable not work after v7.1.0 #50508 said, and use JaegerUI to get trace info success.
  
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

1. It must be approved by the approvers firstly.
2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.1@bc598fa). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #50556   +/-   ##
================================================
  Coverage               ?   73.4139%           
================================================
  Files                  ?       1207           
  Lines                  ?     378702           
  Branches               ?          0           
================================================
  Hits                   ?     278020           
  Misses                 ?      82929           
  Partials               ?      17753           

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [hawkingrei]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-22 08:18:43.319794047 +0000 UTC m=+775964.884091750: ☑️ agreed by hawkingrei.