Use swift-init to kill swift processes.

- That pkill wasn't working.

Change-Id: Ibcb6fc6d9433dca08e0584ae811a2ca276cc469a
diff --git a/stack.sh b/stack.sh
index 87865dc..a568dfd 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1375,7 +1375,7 @@
     install_package memcached
 
     # We make sure to kill all swift processes first
-    pkill -f -9 swift-
+    swift-init all stop || true
 
     # We first do a bit of setup by creating the directories and
     # changing the permissions so we can run it as our user.