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/etc/tempest.conf.sample b/etc/tempest.conf.sample
index cc84994..be05015 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -66,6 +66,9 @@
 # Cluster: the 'nova' user must have scp access between cluster nodes
 resize_available = true
 
+# Level to log Compute API request/response details.
+log_level = ERROR
+
 [image]
 # This section contains configuration options used when executing tests
 # against the OpenStack Images API