Vault CLI makes request to incorrect URL when namespace is both provided as argument and part of the path

[kmehkeri]

Describe the bug
Namespace documentation states that namespace can be treated as part of the path. This works fine with HTTP API, but CLI makes request to incorrect URL when namespace is both provided as argument and part of the path.

To Reproduce

# Setup
vault namespace create dev
vault namespace create -namespace=dev myapp
vault secrets enable -version=2 -namespace=/dev/myapp -path=secrets kv
vault kv put -namespace=/dev/myapp secrets/examplePath foo=APPsecret

# Check that HTTP API works; all below requests return the same result
export VAULT_ADDR=...
export VAULT_TOKEN=...
curl -H "X-Vault-Token: $VAULT_TOKEN" -H "X-Vault-Namespace: " -X GET $VAULT_ADDR/v1/dev/myapp/secrets/data/examplePath
curl -H "X-Vault-Token: $VAULT_TOKEN" -H "X-Vault-Namespace: dev" -X GET $VAULT_ADDR/v1/myapp/secrets/data/examplePath
curl -H "X-Vault-Token: $VAULT_TOKEN" -H "X-Vault-Namespace: dev/myapp" -X GET $VAULT_ADDR/v1/secrets/data/examplePath

# Check CLI
vault kv get -field foo -namespace= dev/myapp/secrets/examplePath  # APPsecret
vault kv get -field foo -namespace=/dev myapp/secrets/examplePath  # No value found at dev/myapp/secrets/data/myapp/secrets/examplePath
vault kv get -field foo -namespace=/dev/myapp secrets/examplePath  # APPsecret

Expected behavior
Command vault kv get -field foo -namespace=/dev myapp/secrets/examplePath should work and return the secret. That is, CLI should call dev/myapp/secrets/data/examplePath instead of dev/myapp/secrets/data/myapp/secrets/examplePath.

Environment:

• Vault Server Version (retrieve with vault status): 1.8.2+ent
• Vault CLI Version (retrieve with vault version): v1.8.2+ent (bf22e1eb262e59f08bb8a1374dc726ab93830178)
• Server Operating System/Architecture: Windows 10 / 5.4.72-microsoft-standard-WSL2

Vault server configuration file(s):

(empty)

Additional context
n/a