Fix chroot builder to work with chef-solo

According to be5adb92b5c4d5d95e5089be94c706b930fea7ba, the UploadDir
method supports two ways of copying depending on whether a trailing
slash is used:
    src = "dir"  -> dest/dir
    src = "dir/" -> dest

On BSD-based systems (such as OSX, FreeBSD, etc.) the `cp -R` command
handles these two cases automatically.  However, Linux treats "src/" and
"src" the same.

To support the trailing slash syntax portably, we can use:
    src = "dir"   -> dest/dir
    src = "dir/." -> dest

This works on BSD and Linux.  It is better than using wildcards as it
grabs hidden files as well.

This fixes #1196 that prevents the chef-solo provisioner from working
with the chroot builder.
Merge pull request #1209 from blt04/fix-chef-solo-chroot

Fix chroot builder to work with chef-solo provisioner. Fixes  #1196