LP1808016: improve error handling by open-ils.pcrud

LP1808016: improve error handling by open-ils.pcrud

This patch ensures that requests to open-ils.pcrud return
an error code (before the request completion code) when
a permissions or constraint check fails.

To test
-------
[1] Make an invalid request, e.g., by attempting to create a claim
    type whose owner is not set in the Acquisitions Claiming admin
    interface.
[2] Note that the user interface reports that the action succeeds
    (although the new claim type is not actually created).
[3] Apply the patch and repeat step 1. This time, the admin interface
    shoudl report that the creation failed.

Signed-off-by: Jane Sandberg <sandbergja@gmail.com>
Signed-off-by: Terran McCanna <tmccanna@georgialibraries.org>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>