Prevent the use of 'swift' in ENABLED_SERVICES

This is not supported and we missed a comment in stackrc that still
said otherwise.  Fix the comment and abort in the sanity check section
if 'swift' is detected in ENABLED_SERVICES.

Change-Id: I78222d7ee2ea8a281962129d5bcf06c118469510
diff --git a/stack.sh b/stack.sh
index 4f7b80e..dff6bd3 100755
--- a/stack.sh
+++ b/stack.sh
@@ -149,6 +149,14 @@
     fi
 fi
 
+# Look for obsolete stuff
+if [[ ,${ENABLED_SERVICES} =~ ,"swift" ]]; then
+    echo "FATAL: 'swift' is not supported as a service name"
+    echo "FATAL: Use the actual swift service names to enable tham as required:"
+    echo "FATAL: s-proxy s-object s-container s-account"
+    exit 1
+fi
+
 # Make sure we only have one rpc backend enabled,
 # and the specified rpc backend is available on your platform.
 check_rpc_backend