This fixes the issue where "childFD" from syscall.Openat is assigned to
a local variable inside the for loop, instead of the correct one in the
function scope. This results in that when trying to close the "childFD"
in the function scope, it will be equal to "-1", instead of the correct
value.
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.
Files in pkg/util/mount that contain significant code implementation for
subpaths are moved to a new package at pkg/volume/util/subpath. This
move is done in order to preserve git history.
