Fix ma certificate functions for chapi.
Fix ma certificate functions for chapi.

Fix ma_create_certificate to actually call the MA to request
certificate creation.

Fix ma_lookup_certificate to return the same values it used to
return. This is NULL if no certificate exists, and only include a
private key in the response if one exists.

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