bail from update_user_keys_on_slivers if there are no AMs found in the slice that support this; avoids later errors
bail from update_user_keys_on_slivers if there are no AMs found in the slice that support this; avoids later errors

tcmitchell/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal