fix reporting of file not found error
fix reporting of file not found error

The callback was getting called with the wrong value resulting the breakpoint
never being updated w/ the error on the server side. This causes the client to
wait upon a breakpoint forever even though we didn't even set the breakpoint in
the debuglet.

matthewloring/cloud-debug-nodejs,ofrobots/cloud-debug-nodejs,DominicKramer/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,DominicKramer/cloud-debug-nodejs,DominicKramer/cloud-debug-nodejs,matthewloring/cloud-debug-nodejs,googleapis/cloud-debug-nodejs,ofrobots/cloud-debug-nodejs,ofrobots/cloud-debug-nodejs,matthewloring/cloud-debug-nodejs