owner: fix new owner updating checkpoint too early with pending DDL (#2252)

[ti-chi-bot]

This is an automated cherry-pick of #2252

What problem does this PR solve?

• DDL lost after owner is killed (kill_owner_with_ddl fails) #1260 was reintroduced into the new owner (released in v5.1.0)

What is changed and how it works?

• Changed the start-ts of DDL puller to checkpoint - 1, to satisfy the open-interval assumption by TiKV.
• Fetch the snapshot of meta data at checkpoint instead of checkpoint-1 avoid overlap between listened DDL events and fetched schema snapshot.

Check List

Tests

• Unit test
• Integration test

Related changes

• Need to cherry-pick to the release branch

Release note

• Fix potential DDL loss when owner crashes while executing DDL

[ti-chi-bot]

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[amyangfei]

/merge

[ti-chi-bot]

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

Commit hash: 50fa3aa

[amyangfei]

/run-integration-tests

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

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[amyangfei]

/run-integration-tests

[codecov-commenter]

Codecov Report

Merging #2291 (0c44694) into release-4.0 (753073a) will increase coverage by 0.6857%.
The diff coverage is 59.3214%.

@@                 Coverage Diff                 @@
##           release-4.0      #2291        +/-   ##
===================================================
+ Coverage      53.7661%   54.4518%   +0.6857%     
===================================================
  Files              153        166        +13     
  Lines            15958      19913      +3955     
===================================================
+ Hits              8580      10843      +2263     
- Misses            6475       8031      +1556     
- Partials           903       1039       +136