Install systemd rule generator for iBFT

When dracut is booted with 'ip=ibft' it'll rename the interface
to ibft*. This will cause error messages during booting as
later on systemd is trying to rename the interface again,
which doesn't work as the interface it busy.
So install a systemd generator for creating a dynamic udev
rule to stop udev from renaming that interface.

References: bnc#880336

Signed-off-by: Hannes Reinecke <hare@suse.de>
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