The iohelper dies on SIGPIPE if the stream is closed before all data
is processed. IMO this should be an error condition for virStreamFinish
according to docs like:

  * This method is a synchronization point for all asynchronous
  * errors, so if this returns a success code the application can
  * be sure that all data has been successfully processed.

However for virStreamAbort, not so much:

  * Request that the in progress data transfer be cancelled
  * abnormally before the end of the stream has been reached.
  * For output streams this can be used to inform the driver
  * that the stream is being terminated early. For input
  * streams this can be used to inform the driver that it
  * should stop sending data.

Without this, virStreamAbort will realistically always error for
active streams like domain console. So, treat the SIGPIPE case
as non-fatal if abort is requested.

Note, this will only affect an explicit user requested abort. An
abnormal abort, like from a server error, always raises an error
in the daemon.