Put heat data files in /var/lib/heat-cfntools

Put heat data files in /var/lib/heat-cfntools

The /var/lib/heat-cfntools directory should be owned by the
heat-cfntools package for whichever distro it is included.

This avoids the problem of heat writing to directories owned
by cloud-init.

For the moment, the part handler will continue to write to
/var/lib/cloud/data to be removed at a later date.

Change-Id: I70b714c70ed146d4f6807850d6e7264c6a4624cd
Fixes: Bug #1105806