client: print more info when leader disconnect

[CabinfeverB]

What problem does this PR solve?

Issue Number: Close #7906

should be merged after #7911

What is changed and how does it work?

Check List

Tests

• Unit test

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot[bot]]

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[codecov[bot]]

Codecov Report

Merging #7907 (6700333) into master (c1eabda) will increase coverage by 0.28%. Report is 2 commits behind head on master. The diff coverage is 87.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7907      +/-   ##
==========================================
+ Coverage   73.32%   73.60%   +0.28%     
==========================================
  Files         435      436       +1     
  Lines       48195    48349     +154     
==========================================
+ Hits        35337    35586     +249     
+ Misses       9784     9718      -66     
+ Partials     3074     3045      -29     

Flag	Coverage Δ
unittests	73.60% <87.50%> (+0.28%)	:arrow_up:

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