The MakeFile and MakeDir methods in the HostUtil interface only had one
caller -- the Host Path volume plugin. This patch relocates MakeFile and
MakeDir to the Host Path plugin itself.
This patch takes all the HostUtil functionality currently found in
mount*.go files and copies it into hostutil*.go files. Care was taken to
preserve git history to the fullest extent.
As part of doing this, some common functionality was moved into
mount_helper files in preperation for HostUtils to stay in k/k and Mount
to move out. THe tests for each relevant function were moved to test
files to match the appropriate location.
