Handle signer certs with no UUID in message handler.
Handle signer certs with no UUID in message handler.

Fix an erroneous check for a signer uuid. If a message has a signer,
build guards and verify authorization. Choose an appropriate
certificate field (uuid, urn) for printing the error message if any
guard fails.

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