Improve combustion script

LeapMicro capo deployments are failing because the combustion script can find the network data file (maybe because of a recent change) and cannot configure network. The script is searching for metal3 keyword to detect if is a CAPM3 deployment or not in order to configure network.

management-cluster-server1:~ # cat /mnt/openstack/latest/meta_data.json
{"local-hostname": "management-cluster-server1", "local_hostname": "management-cluster-server1", "metal3-name": "management-cluster-server1", "metal3-namespace": "sylva-system", "name": "management-cluster-server1", "providerid": "sylva-system/management-cluster-server1/management-cluster-cp-8a52a90ebb-pstlt", "uuid": "cfbd8ddd-1461-4375-b765-7ec3661d073b"}