In acquire_cred_from, probe for remote creds
    
    If the calling application is passing in a cred_store, it's either one of two
    cases:
    - The application previously stored credentials in a ccache and now wants to
    use them.
    - The application has access to specific keys and wants to acquire a local
    credential.
    
    In the first case we can only work with a remote call as a local mechanism
    wouldn't know what to do with remote creds. In the latter calling the remote
    code would make no sense as we have local credentials.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-by: Robbie Harwood <rharwood@redhat.com>