add scaling to callback

Author: jayantk

apps/fortuna/config.sample.yaml

@@ -6,6 +6,8 @@ chains:
     # Keeper configuration for the chain
     reveal_delay_blocks: 0
     gas_limit: 500000
+    # Increase the transaction gas limit by 10% each time the callback fails
+    backoff_gas_multiplier_pct: 110
     min_keeper_balance: 100000000000000000
 
     # Provider configuration