multipath: rely on udev device creation for kpartx

multipath: rely on udev device creation for kpartx

Since kpartx and multipathd don't wait on udev creating the device, there
was a race between libdevmapper and udev to create the device. This meant
that sometimes the /dev/mapper/ devices were devnodes, and sometimes they
were symlinks. Now, for multipathd and kpartx called without -s,
libdevmapper won't create the device nodes, so that udev will always be
responsible for it.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>