Comment 3 for bug 1868817

Looking at the crash, it does discover some config some of the time, but sometimes the probe is returning no data:

 2020-03-27 12:17:30,533 DEBUG curtin:1265 Extracting storage config from probe data
G 2020-03-27 12:17:30,533 WARNING curtin:393 probe_data missing bcache data
 2020-03-27 12:17:30,672 WARNING curtin:393 probe_data missing dasd data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing dmcrypt data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing filesystem data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing lvm data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing raid data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing mount data
 2020-03-27 12:17:30,673 WARNING curtin:393 probe_data missing zfs data
 2020-03-27 12:17:30,673 DEBUG curtin:1272 Sorting extracted configurations
 2020-03-27 12:17:30,673 INFO curtin:1291 Validating extracted storage config components

2020-03-27 12:17:30,698 DEBUG curtin:1325 Merged storage config:
 storage:
     config:
     - id: disk-sda
         path: /dev/sda
         ptable: dos
         serial: 36005076306ffd6b60000000000002603
         type: disk
         wwn: '0x6005076306ffd6b60000000000002603'
     - device: disk-sda
         flag: linux
         id: partition-sda1
         number: 1
         offset: 1048576
         size: 499122176
         type: partition
     version: 1

2020-03-27 12:17:30,700 ERROR root:39 finish: subiquity/Filesystem/_probe/probe_once: FAIL: cancelled
 2020-03-27 12:17:30,704 ERROR block-discover:148 block probing failed restricted=False
 Traceback (most recent call last):
   File "/snap/subiquity/1570/lib/python3.6/site-packages/subiquity/controllers/filesystem.py", line 145, in _probe
     self._probe_once_task.task, 15.0)
   File "/snap/subiquity/1570/usr/lib/python3.6/asyncio/tasks.py", line 351, in wait_for
     yield from waiter
 concurrent.futures._base.CancelledError