Fix vagrant setup broken by commit 7475efbc.

cluster/vagrant/provision-master.sh

@@ -151,10 +151,10 @@ if [[ ! -f "${known_tokens_file}" ]]; then
   # NB: If this list ever changes, this script actually has to
   # change to detect the existence of this file, kill any deleted
   # old tokens and add any new tokens (to handle the upgrade case).
-  local -r service_accounts=("system:scheduler" "system:controller_manager" "system:logging" "system:monitoring" "system:dns")
+  service_accounts=("system:scheduler" "system:controller_manager" "system:logging" "system:monitoring" "system:dns")
   for account in "${service_accounts[@]}"; do
     token=$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64 | tr -d "=+/" | dd bs=32 count=1 2>/dev/null)
-    echo "${token},${account},${account}" >> "${KNOWN_TOKENS_FILE}"
+    echo "${token},${account},${account}" >> "${known_tokens_file}"
   done
 fi