In C++ bulk_write method return real error code instead of -EIO
Changed bulk_write error report logic

Only return wait error (usually -ETIMEOUT/-110) if wait internal
status (assigned in write completion handler) was set to something
except -ENXIO.

-ENXIO is set by default and means no transactions were sent
Merge pull request #128 from toshic/stable

Changed bulk_write error report logic