Remove unnecessary evaluation of outbound context

* At some places we can't reuse evaluated context value. In case
  of big context sizes it saves lots of CPU cycles.
* Added more profiler traces

Change-Id: I07469efd15348c11ec9066928b962fb7a3bef686

mistral/engine/engine_server.py

@@ -13,6 +13,7 @@
 #    limitations under the License.
 
 from oslo_log import log as logging
+from osprofiler import profiler
 
 from mistral import config as cfg
 from mistral.db.v2 import api as db_api
@@ -129,6 +130,7 @@ class EngineServer(service_base.MistralService):
             **params
         )
 
+    @profiler.trace('engine-server-on-action-complete')
     def on_action_complete(self, rpc_ctx, action_ex_id, result_data,
                            result_error, wf_action):
         """Receives RPC calls to communicate action result to engine.

mistral/engine/rpc_backend/rpc.py

@@ -17,6 +17,7 @@ from oslo_config import cfg
 from oslo_log import log as logging
 import oslo_messaging as messaging
 from oslo_messaging.rpc import client
+from osprofiler import profiler
 from stevedore import driver
 
 from mistral import context as auth_ctx
@@ -192,6 +193,7 @@ class EngineClient(base.Engine):
         )
 
     @wrap_messaging_exception
+    @profiler.trace('engine-client-on-action-complete')
     def on_action_complete(self, action_ex_id, result, wf_action=False,
                            async=False):
         """Conveys action result to Mistral Engine.

mistral/workflow/direct_workflow.py

@@ -116,7 +116,7 @@ class DirectWorkflowController(base.WorkflowController):
 
         ctx = data_flow.evaluate_task_outbound_context(task_ex)
 
-        for t_n, params in self._find_next_tasks(task_ex):
+        for t_n, params in self._find_next_tasks(task_ex, ctx=ctx):
             t_s = self.wf_spec.get_tasks()[t_n]
 
             if not (t_s or t_n in commands.RESERVED_CMDS):
@@ -228,12 +228,12 @@ class DirectWorkflowController(base.WorkflowController):
     def _find_next_task_names(self, task_ex):
         return [t[0] for t in self._find_next_tasks(task_ex)]
 
-    def _find_next_tasks(self, task_ex):
+    def _find_next_tasks(self, task_ex, ctx=None):
         t_state = task_ex.state
         t_name = task_ex.name
 
         ctx_view = data_flow.ContextView(
-            data_flow.evaluate_task_outbound_context(task_ex),
+            ctx or data_flow.evaluate_task_outbound_context(task_ex),
             self.wf_ex.context,
             self.wf_ex.input
         )