Because devices will be bind-mounted instead of using `mknod`, we need to make sure the source exists and filter the list by only those whose source is a valid path/current device entry. Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp) Upstream-commit: 9a554e8c37d522ed791b3bb55f9ba9f21e2ac76a Component: engine