Fix typo in thin protocol constants

Author: sharadraju

lib/thin/protocol/constants.js

@@ -48,7 +48,7 @@ module.exports = {
   PURITY_NEW: constants.PURITY_NEW,
   PURITY_SELF: constants.PURITY_SELF,
   SYSASM: constants.SYSASM,
-  SYSBKP: constants.SYSBKP,
+  SYSBKP: constants.SYSBACKUP,
   SYSDBA: constants.SYSDBA,
   SYSDG: constants.SYSDG,
   SYSKM: constants.SYSKM,