[BUG] Password from Env Var Hashed Incorrectly

[terryquigleysas]

What is the bug?
Passwords provided as environment variables are always hashed using BCrypt.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Add password env var to internal_users.yaml - hash: ${envbc.ADMIN_PASSWORD}
2. Change default password hashing algorithm - set plugins.security.password.hashing.algorithm: PBKDF2
3. Start cluster
4. Attempt to connect as user and authentication will fail

What is the expected behavior?
User authenticates

What is your host/environment?

• OpenSearch 2.17

[terryquigleysas]

Please assign to me. I will provide a PR with the fix.