Google's configure-helper.sh script bind-mounts /var/lib/kubelet somewhere
into /home/kubernetes and thus every mount that Kubernetes does is visible
twice in /proc/mounts.

iSCSI and RBD should not rely on counting on entries in /proc/mounts and
unmount device when Kubernetes thinks it's unusued. Kubernetes tracks
the mounts by itself and most of other volume plugins rely on it safely.