[cluster-test] Update private key permissions in terraform
[cluster-test] Update private key permissions in terraform

Closes: #2036
Approved by: sherry-x

libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core