Pre Ready-For-Testing Checklist

• Where is the reproduce steps/test steps documented?
  The reproduce steps/test steps are at:
  [BUG] DR volume failed when synchronizing the incremental backup #6750 (comment)

• Have the backend code been merged (Manager, Engine, Instance Manager, BackupStore etc) (including backport-needed/*)?
  The PR is at
  fix(restore): dr volume failed by delete lock (backport #2183) longhorn-manager#2189

• Which areas/issues this PR might have potential impacts on?
  Area
  Issues

• If labeled: require/automation-e2e Has the end-to-end test plan been merged? Have QAs agreed on the automation test case? If only test case skeleton w/o implementation, have you created an implementation issue (including backport-needed/*)
  The automation skeleton PR is at
  The automation test case PR is at
  The issue of automation test case implementation is at (please create by the template)

Verified pass on longhorn v1.4.x (longhorn-manager c55eaa) with test steps

1. In Longhorn v1.4.x, the DR volume successfully synchronizes the incremental backup.
2. After DR volume is activated, the data is latest data.