Add wc binary-dep to discovery ramdisk
Heat version to latest stable-juno

We need latest stable-juno version of heat, which has for example
fixed stack-update.
Also adding a note about variable needed to be set, so this
reporefs are actually used.
Calling Tuskar CLI properly

As tuskar CLI is added properly here
https://review.openstack.org/#/c/130714/ ,
we can call it properly in instack now.

This was also breaking the packaged install. Fixing also
path for Tuskar templates, which also breaks the packaged
install.