This reverts commit 4bf38a829a.
This variable is pointless since we can always replace it with
/lib/systemd.
Commit I459f7514ab35082d31607968252a9005fa25de2a will fix the issue
in tripleo-image-elements.
Change-Id: I524badb6836a0d04a5f6e6a5b5d95920fd923ef6