Zabbix

.......PS. [ZBXNEXT-10224] simplified zbx_vault_token_lookup_self() by moving error handling to caller functions

Before this change the zbx_vault_token_lookup_self() function was called in
2 places and had error handling to serve different contexts.
It was over-specialized, unsuitable for zbx_vault_renew_token_hashicorp()
which did its own lookup-self request implementation.

This change:
  1) simplifies zbx_vault_token_lookup_self() by moving HTTP response code
     handling out, to caller function. zbx_vault_token_lookup_self() becomes
     minimal and reusable.
  2) modifies the caller function zbx_vault_get_kvs_hashicorp() by adding
     error handling which was formerly in zbx_vault_token_lookup_self().
  3) modifies zbx_vault_renew_token_hashicorp() to use the modified
     zbx_vault_token_lookup_self() instead of internal 'lookup-self' implementation.
  4) removes the 2nd call of zbx_vault_token_lookup_self() from
     zbx_vault_renew_token_hashicorp() in case 'renew-self' request fails.
     zbx_vault_app_role_login_hashicorp() is called straight away, without
     zbx_vault_token_lookup_self().