Remove the requirement to mount disk images on the host
filesystem for file injection, by switching over to use
the new VFS APIs. The mount code is now solely used for
setting up LXC disk images
blueprint: virt-disk-api-refactoring
Change-Id: I1335bf7a8266d3d1d410a66538969f1213766cb9
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>