Update DEVSTACK_SERIES to zed

stable/yoga branch has been created now and
current master is for zed.

Change-Id: I8743a3440a0ce96acb24b34971548b43ae7c8d4c
diff --git a/stackrc b/stackrc
index e48fd81..d22fa88 100644
--- a/stackrc
+++ b/stackrc
@@ -235,7 +235,7 @@
 # Setting the variable to 'ALL' will activate the download for all
 # libraries.
 
-DEVSTACK_SERIES="yoga"
+DEVSTACK_SERIES="zed"
 
 ##############
 #