fix: Address post-deploy Ansible host warnings (#335)
fix: Address post-deploy Ansible host warnings (#335)

The post-deploy task to transfer SSH key pairs and the inventory file to
any client nodes assigned the 'solution_keys' and 'solution_inventory'
roles generates a prominent warning messages when the role is not
present. The dynamic inventory script would only create Ansible groups
for defined roles. This commit create empty 'solution_keys' and
'solution_inventory' Ansible groups in order to suppress the "[WARNING]:
Could not match supplied host pattern" message.
open-power-ref-design-toolkit/cluster-genesis,open-power-ref-design-toolkit/cluster-genesis