metrics(dm): fix lag metrics for ddl never updated

[Ehco1996]

What problem does this PR solve?

Issue Number: close #4471

What is changed and how it works?

if cuurrent max lag is from ddl job, reset this lag after set like skip job

Check List

Tests

• Integration test

Code changes

Side effects

• Possible performance regression
• Increased code complexity

Related changes

Release note

`None`.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lance6716
• lichunzhu

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[lance6716]

rest lgtm

[codecov-commenter]

Codecov Report

Merging #4491 (b1d4c1f) into master (9607554) will decrease coverage by 0.2007%.
The diff coverage is 47.6190%.

Flag	Coverage Δ
cdc	60.0992% <70.5882%> (+0.1770%)	⬆️
dm	51.5585% <34.2465%> (-0.4704%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

@@               Coverage Diff                @@
##             master      #4491        +/-   ##
================================================
- Coverage   55.6402%   55.4394%   -0.2008%     
================================================
  Files           494        498         +4     
  Lines         61283      61624       +341     
================================================
+ Hits          34098      34164        +66     
- Misses        23750      24030       +280     
+ Partials       3435       3430         -5     

[Ehco1996]

could you please take another look for this pr ? thanks 🧡🧡🧡 @lichunzhu

[lichunzhu]

LGTM
But now when DM gets blocked will it increase lag?

[Ehco1996]

LGTM But now when DM gets blocked will it increase lag?

this impl in #4496

[Ehco1996]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b1d4c1f

[Ehco1996]

/run-all-tests

[Ehco1996]

/run-verify