Fix CAHelper MerkleTree building

[sadhbh-c0d3]

Problem

Our CAHelper fails to work correctly for ACL's longer than 2 entries. This needs to be fixed.

Case scenario:

• See IndexDeploymentBuilder::build()
• The withdraw_route_proof is currently skipped (because of that issue)

How to run:

• Run index_deployer app
• See ./scripts/run_index_deployer.sh
• Parameters are: -f ./configs/index_deployment.json -o ./configs/index_maker.json
• Expect program to crash.

About

In the otc-custody library we've got CAHelper class responsible for:

• Building ACL (access control list with addresses and allowed actions)
• Building Merkle Tree (we turn ACL in to merkle tree, Custody ID is the root node)
• Building Merkle Proofs (we take sibling hashes on the branch leading to ACL entry, aka to merkle leaf)