So you can do at max 100 callouts in a transaction.
As I can see you are Setting batch scope as 50. Database.executebatch(objTest, 50);
As you say, for each Account you will be making 12 Folder ie 12 Callouts.
So in each iteration of execute of Batch, you need 12(Folder) *50 (Account) = 600 callouts.
As we cannot do 600 Callouts in execute, you need to change the scope of your batch to the optimal value.
100(Callout)/12(Folder) = 8.3
that means your scope will be 8.
thus the fix will be:
AccountBoxFolderCreationBatch objTest = new AccountBoxFolderCreationBatch();
Database.executebatch(objTest, 8);
Src: Callout limits