fix: override secrets from path

[csatib02]

Overview

• Fixes an issue, with seeing multiple secrets with the same key.

Fixes #202

Notes for reviewers

Functionality is manually tested with the following script:

# Set the Vault address
export VAULT_ADDR="http://127.0.0.1:8200"

# Set the Vault token
export VAULT_TOKEN=227e1cce-6bf7-30bb-2d2a-acc854318caf

export VAULT_TOKEN_FILE=/tmp/vault-token
printf $VAULT_TOKEN > $VAULT_TOKEN_FILE

vault kv put secret/test/mysql MYSQL_PASSWORD=3xtr3ms3cr3t
vault kv put secret/test/aws AWS_ACCESS_KEY_ID=secretId AWS_SECRET_ACCESS_KEY=s3cr3t

# Set secret env-var
export MYSQL_PASSWORD=vault:secret/data/test/mysql#MYSQL_PASSWORD
export AWS_SECRET_ACCESS_KEY=vault:secret/data/test/aws#AWS_SECRET_ACCESS_KEY
export AWS_ACCESS_KEY_ID=vault:secret/data/test/aws#AWS_ACCESS_KEY_ID

export VAULT_FROM_PATH=secret/data/test/aws

# Run secret-init
go build
./secret-init env | grep 'MYSQL_PASSWORD\|AWS_SECRET_ACCESS_KEY\|AWS_ACCESS_KEY_ID'
rm secret-init
rm $VAULT_TOKEN_FILE

[csatib02]

@ramizpolic
I have made the changes on #203, this PR is a follow-up, will fix the conflicts once that is merged.