autobuild[sn-devel-144]: intermittent test failure detected

[autobuild]

The autobuild test system (on sn-devel-144) has detected an intermittent failing test in 
the current master tree.

The autobuild log of the failure is available here:

   http://git.samba.org/autobuild.flakey.sn-devel-144/2017-12-09-2023/flakey.log

The samba build logs are available here:

   http://git.samba.org/autobuild.flakey.sn-devel-144/2017-12-09-2023/samba.stderr
   http://git.samba.org/autobuild.flakey.sn-devel-144/2017-12-09-2023/samba.stdout
  
The top commit at the time of the failure was:

commit 1cbbe18c417533c1edacac23ec98022dd29ef93d
Author: Jamie McClymont <jamiemcclymont at catalyst.net.nz>
Date:   Tue Dec 5 14:51:07 2017 +1300

    s3-selftest: fix creation of large file
    
    The dd command was skipping the first 20MB of /dev/zero then writing only one,
    while indending to create a 20MB sparse file.
    
    Signed-off-by: Jamie McClymont <jamiemcclymont at catalyst.net.nz>
    Reviewed-by: Jeremy Allison <jra at samba.org>
    Reviewed-by: Reviewed-by: Andrew Bartlett <abartlet at samba.org>
    
    Autobuild-User(master): Jeremy Allison <jra at samba.org>
    Autobuild-Date(master): Sat Dec  9 02:56:18 CET 2017 on sn-devel-144