Switch DEVSTACK_SERIES to queens

pike is handled in stable/pike branch for some time
already.

Change-Id: I47dc5bf661c50b3b05c19ad665c2671f807233ae
diff --git a/stackrc b/stackrc
index 0ffcb67..4901009 100644
--- a/stackrc
+++ b/stackrc
@@ -246,7 +246,7 @@
 # Setting the variable to 'ALL' will activate the download for all
 # libraries.
 
-DEVSTACK_SERIES="pike"
+DEVSTACK_SERIES="queens"
 
 ##############
 #