Do not waste too much file system space when running tests

neo/tests/functional/__init__.py

@@ -361,14 +361,23 @@ class NEOCluster(object):
             raise AssertionError('Timeout when starting cluster')
 
     def stop(self, clients=True):
-        error_list = []
+        # Suspend all processes to kill before actually killing them, so that
+        # nodes don't log errors because they get disconnected from other nodes:
+        # otherwise, storage nodes would often flush MB of logs just because we
+        # killed the master first, and waste much file system space.
+        stopped_list = []
         for process_list in self.process_dict.itervalues():
             for process in process_list:
                 try:
-                    process.kill(signal.SIGKILL)
-                    process.wait()
+                    process.kill(signal.SIGSTOP)
+                    stopped_list.append(process)
                 except AlreadyStopped:
                     pass
+        error_list = []
+        for process in stopped_list:
+            try:
+                process.kill(signal.SIGKILL)
+                process.wait()
             except NodeProcessError, e:
                 error_list += e.args
         if clients: