Fix and simplify reboot stress test. Add new env stuff.

Added stress environment var for max_instances.
Added tempest var for log_level of rest_client.

Change-Id: Ia92536a547cdab4d2496bd9ba9067be3595b79cd

xxxxx

Change-Id: I8c2f499a41f74c2fe6fb08c80ab6fc31f6b93426
diff --git a/stress/tests/create_kill.py b/stress/tests/create_kill.py
index 752f72d..8169fc4 100644
--- a/stress/tests/create_kill.py
+++ b/stress/tests/create_kill.py
@@ -32,4 +32,4 @@
                sleep_time=100,  # in milliseconds

                seed=int(time.time()),

                test_name="create and delete",

-               max_vms=32)

+               )