Vault: improve vault server archival/retrieval calls error handling
    
    If a vault operation fails, the error message just says "InternalError". This commit
    improves error handling of key archival and retrieval calls by catching the PKIException
    error and raising it as an IPA error.
    
    Related: https://pagure.io/freeipa/issue/9191
    
    Signed-off-by: Francisco Trivino <ftrivino@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>