Conduit: Improve error handling calling file.uploadchunk/file.querychunks without PHID
Summary: Throw a proper error code and error_info, like similar `file.download` and `file.info` already do.
Test Plan:
* Go to http://phorge.localhost/conduit/method/file.uploadchunk and http://phorge.localhost/conduit/method/file.querychunks , click "Call Method"
* Before this patch, get a generic "ERR-CONDUIT-CORE" error code.
* After this patch, get a "ERR-BAD-PHID" error code and the error info `No such file exists.`
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26754