Vault commands with --enc-dir option leads to directory which doesn't contain VAULT.dat should fail.

Converted credential store storage file is empty but it is very confusing to see successful message and created credential storage file.
The user might mistakenly believe that the VAULT.dat was empty.

How to reproduce
set --enc-dir to folder which is empty.

./elytron-tool.sh   vault --enc-dir /tmp/empty_dir --keystore server.store --keystore-password secretsecret --location converted001.store --alias jboss

Vault (enc-dir="/tmp";keystore="server.store") converted to credential store "converted001.store"