Imported images have an extra './' in the tar file paths. If a later
layer that builds on that import changes a directory to a file or link,
the paths will be different. So this normalizes the paths across all the
layers by stripping off any './' prefix.
Coverage remained the same at 64.65% when pulling 2b22f9ab09154762e78bc9e565e9981386926551 on scanon:issue244 into 4497d28902d797a03d08f9301cec417d1563e2cd on NERSC:master.
Imported images have an extra './' in the tar file paths. If a later layer that builds on that import changes a directory to a file or link, the paths will be different. So this normalizes the paths across all the layers by stripping off any './' prefix.
It adds a test too.
Closes issue #244