btrfs related tests in ubuntu_ecryptfs failed on Precise amd64 / i386

This issue can be reproduced in 3.13.0-142 in proposed and 3.13.0-141. So it should not be considered as a regression.

We didn't have this issue before, until I'm testing 3.13 Precise LTS kernel on the systems (201307-13930 - i386 and 201308-14073 - amd64) in Cert lab instead of using our regular regression-testing test pool from kernel team this cycle.

All btrfs related tests in ubuntu_ecryptfs failed.

miscdev-bad-count.sh.btrfs
extend-file-random.sh.btrfs
trunc-file.sh.btrfs
directory-concurrent.sh.btrfs
file-concurrent.sh.btrfs
lp-994247.sh.btrfs
llseek.sh.btrfs
lp-469664.sh.btrfs
lp-524919.sh.btrfs
lp-509180.sh.btrfs
lp-613873.sh.btrfs
lp-745836.sh.btrfs
lp-870326.sh.btrfs
lp-885744.sh.btrfs
lp-926292.sh.btrfs
inotify.sh.btrfs
mmap-bmap.sh.btrfs
mmap-close.sh.btrfs
mmap-dir.sh.btrfs
read-dir.sh.btrfs
setattr-flush-dirty.sh.btrfs
inode-race-stat.sh.btrfs
lp-911507.sh.btrfs
lp-561129.sh.btrfs
mknod.sh.btrfs
link.sh.btrfs
xattr.sh.btrfs
namelen.sh.btrfs

The output is not really helpful, it's just saying that the return value is 1, like:
03:37:47 DEBUG| Running 'tests/run_one.sh -K -t extend-file-random.sh -b 1000000 -D /mnt/image -l /mnt/lower -u /mnt/upper -f btrfs'
03:37:59 ERROR| Exception escaping from test:
Traceback (most recent call last):
  File "/home/ubuntu/autotest/client/shared/test.py", line 411, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 823, in _call_test_function
    return func(*args, **dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 291, in execute
    postprocess_profiled_run, args, dargs)
  File "/home/ubuntu/autotest/client/shared/test.py", line 212, in _call_run_once
    self.run_once(*args, **dargs)
  File "/home/ubuntu/autotest/client/tests/ubuntu_ecryptfs/ubuntu_ecryptfs.py", line 45, in run_once
    self.results = utils.system_output(cmd, retain_output=True)
  File "/home/ubuntu/autotest/client/shared/utils.py", line 1267, in system_output
    verbose=verbose, args=args).stdout
  File "/home/ubuntu/autotest/client/shared/utils.py", line 918, in run
    "Command returned non-zero exit status")
CmdError: Command <tests/run_one.sh -K -t extend-file-random.sh -b 1000000 -D /mnt/image -l /mnt/lower -u /mnt/upper -f btrfs> failed, rc=1, Command returned non-zero exit status
* Command:
    tests/run_one.sh -K -t extend-file-random.sh -b 1000000 -D /mnt/image -l
    /mnt/lower -u /mnt/upper -f btrfs
Exit status: 1
Duration: 12.1887788773