Fix path to cloudinit directory

Fix path to cloudinit directory

The various path manipulations designed to search for the cloudinit
directory do not work with the current installation script, or when
heat-jeos is also installed. They also perform gratuitous manipulation of
sys.path (causing warning messages) and may pick up the cloudinit files
from a different location to the code that is actually running. Python
already knows which heat package we are using - just look for the directory
inside there.

This patch also tidies up the code for generating the user data.

Change-Id: I14add5f1670aea2562329ff1a1303320a35ff428
Signed-off-by: Zane Bitter <zbitter@redhat.com>