generic/013 in ubuntu_zfs_xfs_generic is not quite stable

[Po-Hsu Lin]

This issue could be found on B-hwe-edge 5.3 ARM64 node "wright-kernel" and B-hwe 5.0 amd64 node "gonzo"

This test, generic/013 from xfstests-dev, in the ubuntu_zfs_xfs_generic test seems not quite stable, sometimes it will fail and cause another 40 tests to fail:
  autotest.ubuntu_zfs_xfs_generic.013
  autotest.ubuntu_zfs_xfs_generic.029
  autotest.ubuntu_zfs_xfs_generic.070
  autotest.ubuntu_zfs_xfs_generic.075
  autotest.ubuntu_zfs_xfs_generic.080
  autotest.ubuntu_zfs_xfs_generic.112
  autotest.ubuntu_zfs_xfs_generic.117
  autotest.ubuntu_zfs_xfs_generic.123
  autotest.ubuntu_zfs_xfs_generic.124
  autotest.ubuntu_zfs_xfs_generic.126
  autotest.ubuntu_zfs_xfs_generic.129
  autotest.ubuntu_zfs_xfs_generic.131
  autotest.ubuntu_zfs_xfs_generic.132
  autotest.ubuntu_zfs_xfs_generic.141
  autotest.ubuntu_zfs_xfs_generic.184
  autotest.ubuntu_zfs_xfs_generic.169
  autotest.ubuntu_zfs_xfs_generic.192
  autotest.ubuntu_zfs_xfs_generic.193
  autotest.ubuntu_zfs_xfs_generic.215
  autotest.ubuntu_zfs_xfs_generic.221
  autotest.ubuntu_zfs_xfs_generic.236
  autotest.ubuntu_zfs_xfs_generic.237
  autotest.ubuntu_zfs_xfs_generic.241
  autotest.ubuntu_zfs_xfs_generic.245
  autotest.ubuntu_zfs_xfs_generic.246
  autotest.ubuntu_zfs_xfs_generic.247
  autotest.ubuntu_zfs_xfs_generic.248
  autotest.ubuntu_zfs_xfs_generic.249
  autotest.ubuntu_zfs_xfs_generic.257
  autotest.ubuntu_zfs_xfs_generic.258
  autotest.ubuntu_zfs_xfs_generic.285
  autotest.ubuntu_zfs_xfs_generic.286
  autotest.ubuntu_zfs_xfs_generic.294
  autotest.ubuntu_zfs_xfs_generic.306
  autotest.ubuntu_zfs_xfs_generic.307
  autotest.ubuntu_zfs_xfs_generic.308
  autotest.ubuntu_zfs_xfs_generic.309
  autotest.ubuntu_zfs_xfs_generic.310
  autotest.ubuntu_zfs_xfs_generic.313
  autotest.ubuntu_zfs_xfs_generic.314
  autotest.ubuntu_zfs_xfs_generic.317

The generic/013 seems to be killed by the time out setting (40min):
 Running: /home/ubuntu/autotest/client/tests/ubuntu_zfs_xfs_generic/ubuntu_zfs_xfs_generic.sh 013 /home/ubuntu/autotest/client/tmp/ubuntu_zfs_xfs_generic/src
 Running '/home/ubuntu/autotest/client/tests/ubuntu_zfs_xfs_generic/ubuntu_zfs_xfs_generic.sh 013 /home/ubuntu/autotest/client/tmp/ubuntu_zfs_xfs_generic/src'
 Creating zfs pool testpool..
 Creating zfs file systems test and scratch in testpool..
 VDEVs in /home/ubuntu/autotest/client/tmp/ubuntu_zfs_xfs_generic/src
 FSTYP -- zfs
 PLATFORM -- Linux/x86_64 gonzo 5.0.0-33-lowlatency #35~18.04.1-Ubuntu SMP PREEMPT Wed Oct 23 06:16:58 UTC 2019
 MKFS_OPTIONS -- testpool/scratch
 MOUNT_OPTIONS -- testpool/scratch /mnt/scratch

Another 40 tests will failed because the pool and test file are in use:
 Creating zfs pool testpool..
 cannot create 'testpool': pool already exists
 Creating zfs file systems test and scratch in testpool..
 cannot create 'testpool/test': dataset already exists
 cannot create 'testpool/scratch': dataset already exists
 umount: /mnt/test: target is busy.
 cannot unmount '/mnt/test': umount failed
 VDEVs in /home/ubuntu/autotest/client/tmp/ubuntu_zfs_xfs_generic/src
 mkdir: cannot create directory ‘/mnt/test’: File exists

[Po-Hsu Lin (cypressyew)]

Sometime one or two retries will make it pass.