Merge pull request #42950 from CongMinYin/fix-dead-lock-during-shutdown

librbd/cache/pwl/ssd: fix dead lock and assert during shutdown

Reviewed-by: Mykola Golub <mykola.golub@clyso.com>
Reviewed-by: Deepika Upadhyay <dupadhya@redhat.com>

diff --cc src/librbd/cache/pwl/AbstractWriteLog.cc
Simple merge

diff --cc src/librbd/cache/pwl/AbstractWriteLog.h
Simple merge

diff --cc src/librbd/cache/pwl/ssd/WriteLog.cc
Simple merge