Add name for instance in Watcher datamodel

Now Watcher's datamodel uses human_id to store the display_name
of the intance. But the value of human_id is not reliable. About
the reason, please see[1].

The solution is to add a 'name' field to save the display_name of
the instance, and ensure that the value of this field is the same
when the datamodel is created and when the datamodel is updated.

About the 'human_id', We will remove it in the future.

References:
[1]. https://bugs.launchpad.net/watcher/+bug/1833665

20190619 Watcher meeting IRC Log:
[1]. http://eavesdrop.openstack.org/irclogs/%23openstack-watcher/%23openstack-watcher.2019-06-19.log.html
[2]. http://eavesdrop.openstack.org/meetings/watcher/2019/watcher.2019-06-19-08.00.log.html#l-47

Change-Id: I6976759629a4feedee09261cc1dac935e050202a
Closes-Bug: #1833665

watcher/decision_engine/model/collector/nova.py

@@ -344,7 +344,10 @@ class ModelBuilder(object):
         flavor = instance.flavor
         instance_attributes = {
             "uuid": instance.id,
+            # TODO(chenker) human_id is deprecated for removal. For the reason,
+            # please reference bug 1833665.
             "human_id": instance.human_id,
+            "name": instance.name,
             "memory": flavor["ram"],
             "disk": flavor["disk"],
             "disk_capacity": flavor["disk"],

watcher/decision_engine/model/notification/nova.py

@@ -71,7 +71,12 @@ class NovaNotification(base.NotificationEndpoint):
         instance.update({
             'state': instance_data['state'],
             'hostname': instance_data['host_name'],
+            # TODO(chenker) human_id is deprecated for removal. For the reason,
+            # please reference bug 1833665.
             'human_id': instance_data['display_name'],
+            # this is the user-provided display name of the server which is not
+            # guaranteed to be unique nor is it immutable.
+            'name': instance_data['display_name'],
             'memory': memory_mb,
             'vcpus': num_cores,
             'disk': disk_gb,

watcher/tests/decision_engine/model/test_element.py

@@ -51,6 +51,7 @@ class TestElement(base.TestCase):
                 'state': 'state',
                 'hostname': 'hostname',
                 'human_id': 'human_id',
+                'name': 'name',
                 'memory': 111,
                 'vcpus': 222,
                 'disk': 333,