This change skips over any devices which does not start with a leading
folder separator ('/'). Allowing such entries causes an OSD to be
created out of the charm directory. This can be caused by something as
innocuous as 2 spaces between devices. The result is that the root
device is also running an OSD, which is undesirable.
Change-Id: I5b52096da0b6f100ae9835c339905585425b27ae
Closes-Bug: 1652175