Leftover devfs entries remain after force lvremove and vgcreate reports "already exists in filesystem" after deleting cache logical volume

Issue

Force removing all LVs in a vg leaves a cache pool devfs entry behind. VG contained just a single cache pool and one origin on top of raid1 when force remove was attempted.

Reproducer:

# lvcreate --activate ey --type raid1 -m 1 -L 100M -n corigin cache_sanity /dev/sda1 /dev/sdb1

# lvcreate --activate ey --type raid1 -m 1 -L 2G -n force_remove cache_sanity /dev/sdc1 /dev/sdd1

# lvcreate --activate ey --type raid1 -m 1 -L 2G -n force_remove_meta cache_sanity /dev/sdc1 /dev/sdd1

# lvconvert --yes --type cache-pool --cachepolicy mq --cachemode writeback -c 32 --poolmetadata cache_sanity/force_remove_meta cache_sanity/force_remove

# lvconvert --yes --type cache --cachemetadataformat 2 --cachepool cache_sanity/force_remove cache_sanity/corigin

# lvremove -ff cache_sanity