VMware: prevent image snapshot if no root disk defined

If there is no root disk defined then the snapshot should
throw an exception.

Change-Id: I0549b8ca9ba41b734277600cb66a74b27ca72d88
Related-bug: #1297605

nova/tests/virt/vmwareapi/test_driver_api.py

@@ -1012,6 +1012,12 @@ class VMwareAPIVMTestCase(test.NoDBTestCase):
         self._create_vm()
         self._test_snapshot()
 
+    def test_snapshot_no_root_disk(self):
+        self._iso_disk_type_created(instance_type='m1.micro')
+        self.assertRaises(error_util.NoRootDiskDefined, self.conn.snapshot,
+                          self.context, self.instance, "Test-Snapshot",
+                          lambda *args, **kwargs: None)
+
     def test_snapshot_non_existent(self):
         self._create_instance()
         self.assertRaises(exception.InstanceNotFound, self.conn.snapshot,

nova/virt/vmwareapi/error_util.py

@@ -149,6 +149,10 @@ class MissingParameter(VMwareDriverException):
     msg_fmt = _("Missing parameter : %(param)s")
 
 
+class NoRootDiskDefined(VMwareDriverException):
+    msg_fmt = _("No root disk defined.")
+
+
 class AlreadyExistsException(VMwareDriverException):
     msg_fmt = _("Resource already exists.")
     code = 409

nova/virt/vmwareapi/vmops.py

@@ -760,6 +760,10 @@ class VMwareVMOps(object):
             (vmdk_file_path_before_snapshot, adapter_type,
              disk_type) = vm_util.get_vmdk_path_and_adapter_type(
                                         hw_devices, uuid=instance['uuid'])
+            if not vmdk_file_path_before_snapshot:
+                LOG.debug("No root disk defined. Unable to snapshot.")
+                raise error_util.NoRootDiskDefined()
+
             datastore_name = ds_util.split_datastore_path(
                                         vmdk_file_path_before_snapshot)[0]
             os_type = self._session._call_method(vim_util,