NCBC-705: ensure that servers error message is returned when view request fails

When a view request errors out, the results that are being returned:

{"error":"not_found","reason":"Design document _design/beer-sample2 not
found"}

Are overridden by the error handling logic, and return back a more generic
.NET error: (404) Not Found. This patch ensures that the servers error
message is preserved and returned back to the caller.

Change-Id: Iae0cff849c2d6f3d1929604ef83baae26e993079
Reviewed-on: http://review.couchbase.org/42585
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Simon Baslé <simon@couchbase.com>