Update DEVSTACK_SERIES to train

stable/stein branch has been created now and
current master is for train.

Change-Id: I119f0388891db44c9753e49cedfeb32c74f2a40d
diff --git a/stackrc b/stackrc
index c6304bb..2924d39 100644
--- a/stackrc
+++ b/stackrc
@@ -258,7 +258,7 @@
 # Setting the variable to 'ALL' will activate the download for all
 # libraries.
 
-DEVSTACK_SERIES="stein"
+DEVSTACK_SERIES="train"
 
 ##############
 #