Add missing cloud/region/az/host_id info to nodes

To the greatest extent possible within the limitation of each provider,
this adds cloud, region, az, and host_id to nodes.

Each of AWS, Azure, GCE, IBMVPC have the cloud name hard-coded to
a value that makes sense for each driver given that each of these
are singleton clouds.  Their region and az values are added as
appropriate.

The k8s, openshift, and openshiftpods all have their cloud names set
to the k8s context name, which is the closest approximation of what
the "cloud" attribute means in its existing usage in the OpenStack
driver.  If pods are launched, the host_id value is set to the k8s
host node name, which is an approximation of the existing usage in
the OpenStack driver (where it is typically an opaque uuid that
uniquely identifies the hypervisor).

Change-Id: I53765fc3914a84d2519f5d4dda4f8dc8feda72f2

nodepool/driver/statemachine.py

@@ -157,6 +157,7 @@ class StateMachineNodeLauncher(stats.StatsReporter):
         node.public_ipv4 = instance.public_ipv4
         node.private_ipv4 = instance.private_ipv4
         node.public_ipv6 = instance.public_ipv6
+        node.cloud = instance.cloud
         node.region = instance.region
         node.az = instance.az
         node.driver_data = instance.driver_data
@@ -737,6 +738,7 @@ class Instance:
     * public_ipv4: str
     * public_ipv6: str
     * private_ipv4: str
+    * cloud: str
     * az: str
     * region: str
     * driver_data: any
@@ -759,6 +761,7 @@ class Instance:
         self.public_ipv6 = None
         self.private_ipv4 = None
         self.interface_ip = None
+        self.cloud = None
         self.az = None
         self.region = None
         self.metadata = {}