framework/execution: ExecutionContext enhancements

- Add workload property as the shortcut for accessing the workoad for
  the current job.
- Add set_status method that setts the status of the current job.
- Add get_metric method that searches for a metric in the output for the
  current job, or failing that, in the run output.

wa/framework/execution.py

@@ -75,6 +75,11 @@ class ExecutionContext(object):
             return True
         return self.current_job.spec.id != self.next_job.spec.id
 
+    @property
+    def workload(self):
+        if self.current_job:
+            return self.current_job.workload
+
     @property
     def job_output(self):
         if self.current_job:
@@ -150,6 +155,11 @@ class ExecutionContext(object):
         self.output.write_result()
         self.current_job = None
 
+    def set_status(self, status):
+        if not self.current_job:
+            raise RuntimeError('No jobs in progress')
+        self.current_job.status = Status(status)
+
     def extract_results(self):
         self.tm.extract_results(self)
 
@@ -171,6 +181,14 @@ class ExecutionContext(object):
     def write_state(self):
         self.run_output.write_state()
 
+    def get_metric(self, name):
+        try:
+            return self.output.get_metric(name)
+        except HostError:
+            if not self.current_job:
+                raise
+            return self.run_output.get_metric(name)
+
     def add_metric(self, name, value, units=None, lower_is_better=False,
                    classifiers=None):
         if self.current_job: