Remove target_power_state

Maybe this is useful for tracking power transition, but seems we
should expose task_state or something else to users instead of
just using ironic's feild, this is the first step of refactoring.

Change-Id: Ibe83f3bfd534e2600769f39045da4d2812ebf5e1

api-ref/source/v1/instances.inc

@@ -296,8 +296,7 @@ Instance Management (instances)
 Instances can be managed through several sub-resources.
 
 A Instance can be rebooted, turned on, or turned off by requesting a change to
-its power state. This is handled asynchronously and tracked in the
-``target_power_state`` field after the request is received.
+its power state. This is handled asynchronously.
 
 
 Instance State Summary
@@ -322,7 +321,6 @@ Response
 .. rest_parameters:: parameters.yaml
 
     - power_state: power_state
-    - target_power_state: target_power_state
 
 **Example instance state:**
 

api-ref/source/v1/parameters.yaml

@@ -210,13 +210,6 @@ project_id_body:
   in: body
   required: true
   type: string
-target_power_state:
-  description: |
-    If a power state transition has been requested, this field represents the
-    requested (ie, "target") state.
-  in: body
-  required: true
-  type: string
 type_description:
   description: |
     The description of the type.

api-ref/source/v1/samples/instances/instance-get-state-response.json

@@ -1,4 +1,3 @@
 {
-  "power_state": "power off",
-  "target_power_state": null
+  "power_state": "power off"
 }

mogan/api/controllers/v1/instances.py

@@ -85,15 +85,11 @@ class InstanceStates(base.APIBase):
     # Just support power state at present.
     # We can expend other fields for other type state.
     power_state = wtypes.text
-    """Represent the current (not transition) power state of the instance"""
-
-    target_power_state = wtypes.text
-    """The user modified desired power state of the instance."""
+    """Represent the current power state of the instance"""
 
     @classmethod
     def sample(cls):
-        sample = cls(target_power_state=ir_states.POWER_ON,
-                     power_state=ir_states.POWER_ON)
+        sample = cls(power_state=ir_states.POWER_ON)
         return sample