Support authentication against Redis

[robertvolkmann]

Description

Clients have to authenticated against Redis in Broadcom SONiC.

{
    "INSTANCES": {
        "redis2": {
            "unix_socket_path": "/var/run/redis/redis2.sock",
            "password_path": "/run/redis/auth/passwd"
        }
    },
    "DATABASES": {
        "APPL_DB": {
            "id": 0,
            "separator": ":",
            "instance": "redis2"
        }
    }
}

[iljarotar]

Seems to work fine in the test environment.