Green GC should scan offline stores

[youjiali1995]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create a cluster which max_replica_count is 1.
2. Scale out one store. It becomes offline.
3. Green GC doesn't scan locks from offline stores. If some regions haven't been transferred to other stores before checking lock observer, these locks are left.

2. What did you expect to see? (Required)

All locks are resolved.

3. What did you see instead (Required)

Locks on offline stores are left.

4. Affected version (Required)

v4.0.x

5. Root Cause Analysis

Green GC doesn't scan offline stores. Locks on these stores may be left.