Update DEVSTACK_SERIES to ussuri

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

Change-Id: I2bb84cb4b32e344572a7c3e6f300c1aa19e486df
diff --git a/stackrc b/stackrc
index 10117f2..e8ee4e0 100644
--- a/stackrc
+++ b/stackrc
@@ -258,7 +258,7 @@
 # Setting the variable to 'ALL' will activate the download for all
 # libraries.
 
-DEVSTACK_SERIES="train"
+DEVSTACK_SERIES="ussuri"
 
 ##############
 #