fix: continue leader failed should close leader component

[yannan]

多副本情况下，某副本作为leader续期失败之后，其作为leader的相关component没有关闭。导致多个副本会同时执行相关任务，直观表现为会存在多个dispatch和watchdog同时执行

[yannan]

~

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 60.31%. Comparing base (e6c7544) to head (369e880).
Report is 1 commits behind head on master.

❗ Current head 369e880 differs from pull request most recent head ab356e3. Consider uploading reports for the commit ab356e3 to get more accurate results

Files	Patch %	Lines
fastflow.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   60.02%   60.31%   +0.28%     
==========================================
  Files          28       28              
  Lines        2972     2986      +14     
==========================================
+ Hits         1784     1801      +17     
+ Misses       1045     1043       -2     
+ Partials      143      142       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ShiningRush]

@yannan 代码没问题，还麻烦补充下关于LeaderChangedHandler close 逻辑的单元测试