Add num_retries configuration option

The boto library is designed for retrying failed actions automatically.

Bug #1089764

Change-Id: I4a42a87286e7d86e6569fa82c7309f2ea5fbfed9
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 020baa1..7ff458a 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -257,6 +257,9 @@
 #TCP/IP connection timeout
 http_socket_timeout = 5
 
+#Number of retries actions on connection or 5xx error
+num_retries = 1
+
 # Status change wait timout
 build_timeout = 120