Inventory file options for metrics nodeselector not correct

[netzzer]

For the choice of [4] and 3 nodes metrics nodeselector is not correct. All other scenarios should be checked as well for this error. This issue has been fixed more than one time and it is back again.

- openshift_metrics_hawkular_nodeselector:{"region":"infra"}
- openshift_metrics_cassandra_nodeselector:{"region":"infra"}
- openshift_metrics_heapster_nodeselector:{"region":"infra"}

+ openshift_metrics_hawkular_nodeselector={"region":"infra"}
+ openshift_metrics_cassandra_nodeselector={"region":"infra"}
+ openshift_metrics_heapster_nodeselector={"region":"infra"}

[netzzer]

Fixed with PR#17