etcdserverpb: update comment for txn request

etcdserver/etcdserverpb/rpc.proto

@@ -127,11 +127,10 @@ message Compare {
   }
 }
 
-// First all the compare requests are processed.
-// If all the compare succeed, all the success
-// requests will be processed.
-// Or all the failure requests will be processed and
-// all the errors in the comparison will be returned.
+// If the comparisons succeed, then the success requests will be processed in order, 
+// and the response will contain their respective responses in order.
+// If the comparisons fail, then the failure requests will be processed in order, 
+// and the response will contain their respective responses in order.
 
 // From google paxosdb paper:
 // Our implementation hinges around a powerful primitive which we call MultiOp. All other database