aio-dio-append-write-read-race: abort if we encounter syscall errors

aio-dio-append-write-read-race: abort if we encounter syscall errors

If any of the library calls return error codes, just print out a message
and abort the test.  Whoever wrote the write test did not check for
write failures, which means that if we ENOSPC without writing anything
then the reader thread will loop forever trying to read.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>