Simplify service definition

Do not care about init_style this should chef know automatically.

I wonder why the present construct is there, to me this looks like a correct solution. If you agree, I'll also change it for other services, not just osd.
If TK is OK without it, there is no reason to keep it.

I created it myself some years ago because Ceph packaging wasn't that good.
It's not the same anymore.