Allow use of a single path if multipath activation fails. (#1054806)

If multipath loses the race to claim the member disks and something
like lvm activates devices on one of the members, allow direct use
of that member and ignore the others. This allows configuration to
continue, but without the benefits of multipath.
Let the udev queue settle before populating the devicetree. (#1049772)

In this case we open a LUKS device from the custom spoke in anaconda
and then call populate, but an LVM PV on the opened LUKS device can
take some time to get setup.

(cherry picked from commit bd8860248ab3c4a7af2997090526f6ced953b1e3)