failpoint: avoid returning the undeclared error

[shafreeck]

Signed-off-by: Shafreeck Sea shafreeck@gmail.com

What problem does this PR solve?

Some unuseful messages are printed

failpoint is disabled on xxx

What is changed and how it works?

• Return errors directly for failpoints.Eval
• Add more checks before printing the log message
• Print error with the failpath

Check List

Tests

• Unit test
• Integration test

[codecov[bot]]

Codecov Report

Merging #54 into master will decrease coverage by 0.2939%. The diff coverage is 84.6153%.

@@               Coverage Diff                @@
##             master        #54        +/-   ##
================================================
- Coverage   86.0082%   85.7142%   -0.2940%     
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  Files             7          7                
  Lines           972        980         +8     
================================================
+ Hits            836        840         +4     
- Misses           84         86         +2     
- Partials         52         54         +2