PAPR: customize disk space requirements

Currently the job reports only 1.7 GB free and it has been able to
perform installs, so setting the requirement down to 1.5 GB.

.papr.inventory

@@ -9,6 +9,7 @@ ansible_python_interpreter=/usr/bin/python3
 deployment_type=origin
 openshift_image_tag="{{ lookup('env', 'OPENSHIFT_IMAGE_TAG') }}"
 openshift_master_default_subdomain="{{ lookup('env', 'RHCI_ocp_node1_IP') }}.xip.io"
+openshift_check_min_host_disk_gb=1.5
 openshift_check_min_host_memory_gb=1.9
 
 [masters]