Fix building mysql element on non-upstart systems
Fix building mysql element on non-upstart systems

Without this change we fail to build the element because /etc/init does
not exist.

Change-Id: I7b7c81e263e1105f82f6d4c1a91ab74103d8aa3f

openstack/tripleo-image-elements,radez/tripleo-image-elements,rdo-management/tripleo-image-elements,rdo-management/tripleo-image-elements,openstack/tripleo-image-elements,radez/tripleo-image-elements