BUG #13888: pg_dump write error

The following bug has been logged on the website:

Bug reference:      13888
Logged by:          Vladimir Kunschikov
Email address:      kunschikov@gmail.com
PostgreSQL version: 9.4.5
Operating system:   Linux
Description:

Database backup in heavy loaded environment sometimes fails with the
following error:

 pg_dump: [parallel archiver] could not write to output file: Success

Subsequent rerun of the pg_dump solves that problem.
More elegant and reliable solution:  WRITE_ERROR_EXIT macro replacement in
ahwrite() function at src/bin/pg_dump/pg_backup_archiver.c source file.
There can be some error checking instead of this macro.