Fix T46042: Netrender: Slave continues to render frames after cancellation by job manager.

To be backported to 2.78.

netrender/slave.py

@@ -322,9 +322,6 @@ def render_slave(engine, netsettings, threads):
                 if job.type == netrender.model.JOB_BLENDER:
                     netrender.repath.reset(job)
 
-                # read leftovers if needed
-                data.stdout += process.stdout.read()
-
                 if data.cancelled:
                     # kill process if needed
                     if process.poll() is None:
@@ -334,6 +331,9 @@ def render_slave(engine, netsettings, threads):
                             pass
                     continue # to next frame
 
+                # read leftovers if needed
+                data.stdout += process.stdout.read()
+
                 # flush the rest of the logs
                 if data.stdout:
                     stdout_text = str(data.stdout, encoding='utf8')