skip udev: event - keep one rtnl per worker, rather than per event

This commit follows upstream's

    4c83d994566718043e61e568cc214bdc4587f869

We adopt their removal of excessive logging, but we do not switch
to one rtnl per worker, rather than per event.  This maintains
code separation between libsystemd and udev code.  The disadvantage
is that we do not get the cost savings of having one rtnl per
worker rather than per event.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>