traceapp: let errors in HTTP handlers bubble up properly.
traceapp: let errors in HTTP handlers bubble up properly.

As it turns out by looking at handler.go -- we should've returned the
errors in these functions directly rather than invoking http.Error
directly, as handler.go has any HTTP handler returning errors logged
and subsequently return via the http.Error function.

bg451/appdash,bg451/appdash,bg451/appdash,joeshaw/appdash,joeshaw/appdash,joeshaw/appdash