xci: idf: Add more information for installers and flavors

xci: idf: Add more information for installers and flavors

Each installer has its own Ansible groups so we need record such
information separately. Moreover, we need to add 'flavor' information
to the IDF so we know which hosts belong to what flavor. This also
fixes the kubernetes installer type to be 'kubespray' instead of 'k8s'
Finally, we extend the IDF to also set appropriate hostnames for the
nodes.

Change-Id: I52b20908ad927840e0b38fba96be8faf6da2b52d
Signed-off-by: Markos Chandras <mchandras@suse.de>