PersistentVolume for gcsfuse mount not being removed on kctf chal stop

when doing `kctf chal stop`, the pv for a challenge does not appear to be getting removed.

this subsequently causes `kctf chal start` to fail,

we've been having to run `kubectl delete pv $pv_name` after `kctf chal stop` to get it to work

-- todo: add some logs later, just opening issue for now