Extended GetMountMedium function to check if hugetlbfs volume
is mounted with the page size equal to the medium size.
Page size is obtained from the 'pagesize' mount option of the
mounted hugetlbfs volume.
This patch removes pkg/util/mount completely, and replaces it with the
mount package now located at k8s.io/utils/mount. The code found at
k8s.io/utils/mount was moved there from pkg/util/mount, so the code is
identical, just no longer in-tree to k/k.