plugin/builder-amazon-chroot: add test file
builder/amazon/chroot: perform early cleanup
builder/amazon/chroot: initial len should be 0 so we don't have empty
builder/amazon/chroot: step to snapshot the root image
communicator/ssh: log when remote exits
builder/amazon/chroot: log the exit code for the chroot communicator
builder/amazon/common: correct the log statement
builder/amazon/chroot: switch func type to interface

Was getting weird behavior... see
https://groups.google.com/d/msg/golang-nuts/a1kymwSVt2M/FwcCuBl1_48