Do a proper tls/ca cleanup in unstack

Certificates and the index were left in the data directory after
running unstack. That would break devstack on the next run.

partial blueprint devstack-https
Change-Id: I6eb552a76fb29addf4d02254c027e473d6805df1
diff --git a/unstack.sh b/unstack.sh
index a5e7b87..fe5fc77 100755
--- a/unstack.sh
+++ b/unstack.sh
@@ -122,9 +122,10 @@
     stop_horizon
 fi
 
-# Kill TLS proxies
+# Kill TLS proxies and cleanup certificates
 if is_service_enabled tls-proxy; then
-    killall stud
+    stop_tls_proxy
+    cleanup_CA
 fi
 
 SCSI_PERSIST_DIR=$CINDER_STATE_PATH/volumes/*