use 'auto' instead of None

In cli cmds:watcher audit create,
the Strategy is None if no --strategy
It's better to use default instead of None
watcher audit create -g thermal_optimization
+-------------+--------------------------------------+
| Field       | Value                                |
+-------------+--------------------------------------+
| UUID        | 2bc3001d-683a-48ee-b2f2-766cb8d6329e |
| Created At  | 2016-12-22T08:41:21.173601+00:00     |
| Updated At  | None                                 |
| Deleted At  | None                                 |
| State       | PENDING                              |
| Audit Type  | ONESHOT                              |
| Parameters  | {}                                   |
| Interval    | None                                 |
| Goal        | thermal_optimization                 |
| Strategy    | None                                 |
| Audit Scope | []                                   |
+-------------+--------------------------------------+

Change-Id: I5798df81303c425ed0e26e401589e6680b945bf6

watcherclient/tests/v1/test_audit_shell.py

@@ -78,7 +78,7 @@ AUDIT_2 = {
     'audit_template_uuid': 'f8e47706-efcf-49a4-a5c4-af604eb492f2',
     'audit_template_name': 'at1',
     'goal_name': 'fc087747-61be-4aad-8126-b701731ae836',
-    'strategy_name': None,
+    'strategy_name': 'auto',
     'created_at': datetime.datetime.now().isoformat(),
     'updated_at': None,
     'deleted_at': None,
@@ -94,7 +94,7 @@ AUDIT_3 = {
     'audit_template_uuid': 'f8e47706-efcf-49a4-a5c4-af604eb492f2',
     'audit_template_name': 'at1',
     'goal_name': None,
-    'strategy_name': None,
+    'strategy_name': 'auto',
     'created_at': datetime.datetime.now().isoformat(),
     'updated_at': None,
     'deleted_at': None,

watcherclient/v1/audit_shell.py

@@ -41,6 +41,8 @@ class ShowAudit(command.ShowOne):
 
         try:
             audit = client.audit.get(parsed_args.audit)
+            if audit.strategy_name is None:
+                audit.strategy_name = 'auto'
         except exceptions.HTTPNotFound as exc:
             raise exceptions.CommandError(str(exc))
 
@@ -115,6 +117,9 @@ class ListAudit(command.Lister):
 
         try:
             data = client.audit.list(**params)
+            for audit in data:
+                if audit.strategy_name is None:
+                    audit.strategy_name = 'auto'
         except exceptions.HTTPNotFound as ex:
             raise exceptions.CommandError(str(ex))
 
@@ -189,6 +194,8 @@ class CreateAudit(command.ShowOne):
                     fields['strategy']).uuid
 
         audit = client.audit.create(**fields)
+        if audit.strategy_name is None:
+            audit.strategy_name = 'auto'
 
         columns = res_fields.AUDIT_FIELDS
         column_headers = res_fields.AUDIT_FIELD_LABELS