add some tests for host and seperate negative ones

For host operation, there are some APIs: list, show, update, startup,
shutdown, reboot. This patch will mainly add some negative tests for
update, startup, shutdown, reboot. It is important to note that, for
Libvirt Driver currently, there are no implementations for
set_host_enabled/host_maintenance_mode/host_power_action.

Change-Id: Ia810b956a20eae67e8ec43e3edf9fcb019f71711
diff --git a/tempest/services/compute/json/hosts_client.py b/tempest/services/compute/json/hosts_client.py
index 30a3f7b..f51879d 100644
--- a/tempest/services/compute/json/hosts_client.py
+++ b/tempest/services/compute/json/hosts_client.py
@@ -44,3 +44,39 @@
         resp, body = self.get("os-hosts/%s" % str(hostname))
         body = json.loads(body)
         return resp, body['host']
+
+    def update_host(self, hostname, **kwargs):
+        """Update a host."""
+
+        request_body = {
+            'status': None,
+            'maintenance_mode': None,
+        }
+        request_body.update(**kwargs)
+        request_body = json.dumps(request_body)
+
+        resp, body = self.put("os-hosts/%s" % str(hostname), request_body,
+                              self.headers)
+        body = json.loads(body)
+        return resp, body
+
+    def startup_host(self, hostname):
+        """Startup a host."""
+
+        resp, body = self.get("os-hosts/%s/startup" % str(hostname))
+        body = json.loads(body)
+        return resp, body['host']
+
+    def shutdown_host(self, hostname):
+        """Shutdown a host."""
+
+        resp, body = self.get("os-hosts/%s/shutdown" % str(hostname))
+        body = json.loads(body)
+        return resp, body['host']
+
+    def reboot_host(self, hostname):
+        """reboot a host."""
+
+        resp, body = self.get("os-hosts/%s/reboot" % str(hostname))
+        body = json.loads(body)
+        return resp, body['host']