The PV name is often necessary to build correct symlink paths
/var/lib/kubelet/pods/{podUid}}/{DefaultKubeletVolumeDevicesDirName}/{escapeQualifiedPluginName}/{PV name}
This patch cleans up pkg/util/mount/* and pkg/util/volume/* to always
use filepath.Join instead of path.Join. filepath.Join is preferred
because path.Join can have issues on Windows.