As part of moving pkg/util/mount out of tree, the NSEnter implementation
of mount.Interface needs to be relocated out of pkg/util/mount, as it is
K8s specific. This patch relocates that mounter implementation to
pkg/volume/util/nsenter.
Since the NSEnter mounter shares a lot of its logic with the Linux
mounter implementation, many of the previously private methods of the
Linux mounter are now made public to maintain that shared code.
Additionaly, it was observed that *all* mount.Interface implemenations
were using the same common method for IsNotMountPoint, so this patch
removes that method from the mount.Interface definition and just exports
the common implementation instead.
fix log warning
use IsCorruptedMnt in GetMountRefs on Windows
use errorno in IsCorruptedMnt check
fix comments: add more error code
add more error no checking
change year
fix comments
