Appending wildcard to src causes problems

It appears that the desired effect was to support
    src = "dir" -> dest/dir
    src = "dir/" -> dest

but cp -R already handles this, provided the trailing slash does not
get consumed by the shell.

The wildcard causes problems when multiple files match the
shell glob, e.g.

UploadDir("/tmp", "./salt*", [])

where my working dir contains
 - salt
 - salt-foo

will error.
Merge pull request #1111 from njhartwell/master

builder/amazon/chroot: Appending wildcard to src causes problems