Add feature to get password from Vault

[Dmitry-Eremeev]

To use the feature put the following options in config root: use_vault: true vault_address: http://<IP_ADDRESS:<IP_PORT> vault_role_id: <ROLE_ID> vault_secret_id: <SECRET_ID> vault_secret_path: <deployments/dev/user/passwords_yml> vault_secret_mount_path: <secret_v2> credential_name_in_vault_secret: <keystone_admin_password>

Closes https://github.com/openstack-exporter/openstack-exporter/issues/412

[Sharpz7]

I think the issue is https://github.com/openstack-exporter/openstack-exporter/pull/437, and potentially something else. I will look into it myself at some point but if you have free time feel free to cover and I can quickly get it merged. Again, apologies for the random closing.