Add pkrvars example file

openstack.pkrvars.hcl.example

+# Favor to use
+flavor = "m1.small"
+# Source image to build off of - current support with ansible assumes Centos 7
+source_image = "some-CentOS-7-image"
+# Floating IP network - one will be assigned in order to provision the image
+floating_ip_network = "floating-network-name"
+# A uuid list of network(s) that the instance should be created in
+networks = ["aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"]
+# Security group sto add to the instance - you should add at least one that provides ssh access to the machine
+security_groups = ["allow ssh"]
+# set to 'true' to append a YYYYMMDDHHmm suffix to the image created
+image_date_suffix = false
+# Set to a public key that will be added as a root ssh key
+root_ssh_key = "ecdsa-sha2-nistp256 AAAAyourkeyhere comment string here"