Support for HP Cloud

This plugin enables the ohai attributes for HP Cloud in the same way as the EC2 plugin.

HP Cloud is currently in private beta, however the relevant output is follows:

  "hpcloud": {
    "public_hostname": "xxxxx.xxx.xxx",
    "placement_availability_zone": "nova",
    "block_device_mapping_root": "/dev/vda",
    "mpi_base": "10.4.8.216 slots=1\n10.4.8.215 slots=1\n10.4.8.213 slots=1\n10.4.7.55 slots=2\n10.4.7.50 slots=4\n10.4.6.62 slots=2\n10.4.6.75 slots=1",
    "instance_action": "none",
    "public_keys_0_openssh_key": "ssh-rsa AAAAB3Nz...",
    "instance_id": "i-nnnnnnnn",
    "instance_type": "standard.medium",
    "local_ipv4": "nnn.nnn.nnn.nnn",
    "block_device_mapping_ephemeral0": "/dev/vdb",
    "local_hostname": "xxxxx.xxx.xxx",
    "kernel_id": "aki-000004d7",
    "public_ipv4": "nnn.nnn.nnn.nnn",
    "reservation_id": "xxnnnnn",
    "hostname": "xxxxx.xxx.xxx",
    "ami_id": "ami-000004d8",
    "userdata": "",
    "block_device_mapping_ami": "vda",
    "ami_launch_index": "0",
    "security_groups": [
      "default"
    ],
    "ami_manifest_path": "FIXME"
  }

This has been tested across multiple nodes including after distribution with Chef