Abort waitForReadyRead() when there is an error

When in readNotification() or completeAsyncWrite() an error
is emitted and the loop is not exited, this error signal
will flood the eventloop.

Change-Id: I77b8a4c337041258862b19a07917bef059c11cc1
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>