storage: export zpools unconditionally

In the _pre_shutdown function, we used to invoke `zpool export -a` if we
found the presence of a zpool in the storage model.

That being said, zpools can be implicitly declared by users using
{"type": "format", "fstype": "zfsroot"} in the curtin actions. This is
valid curtin configuration and unfortunately causes Subiquity to think
that there is no zpool.

When that happened, Subiquity did not invoke `zpool export -a` and
therefore the target system couldn't boot without a call to `zpool
import -f`.

We now do the call to `zpool export -a` unconditionally. Running this
command when there is no zpool is a noop so it should not be a problem.

In theory there is a risk that we could export a zpool that was not
meant for exporting. However, that would involve somebody importing (or
force importing) a zpool in the live installer environment and not
wanting it exported at the end. This sounds like an very unlikely use
case. Furthermore, this could already be a problem today since we invoke
`zpool export` with the `-a` option (which all pools imported on the
system).

LP: #2073772

Signed-off-by: Olivier Gayot <[email protected]>
(cherry picked from commit 2906431)

subiquity/server/controllers/filesystem.py

@@ -1657,5 +1657,4 @@ async def _pre_shutdown(self):
                 )
             else:
                 await self.app.command_runner.run(["umount", "--recursive", "/target"])
-        if len(self.model._all(type="zpool")) > 0:
-            await self.app.command_runner.run(["zpool", "export", "-a"])
+        await self.app.command_runner.run(["zpool", "export", "-a"])

subiquity/server/controllers/tests/test_filesystem.py

@@ -361,9 +361,10 @@ async def test__pre_shutdown_install_started(self):
             [
                 mock.call(["mountpoint", "/target"]),
                 mock.call(["umount", "--recursive", "/target"]),
+                mock.call(["zpool", "export", "-a"]),
             ]
         )
-        self.assertEqual(len(mock_run.mock_calls), 2)
+        self.assertEqual(3, mock_run.call_count)
 
     async def test__pre_shutdown_install_not_started(self):
         async def fake_run(cmd, **kwargs):
@@ -372,10 +373,15 @@ async def fake_run(cmd, **kwargs):
 
         self.fsc.reset_partition_only = False
         run = mock.patch.object(self.app.command_runner, "run", side_effect=fake_run)
-        _all = mock.patch.object(self.fsc.model, "_all")
-        with run as mock_run, _all:
+        with run as mock_run:
             await self.fsc._pre_shutdown()
-        mock_run.assert_called_once_with(["mountpoint", "/target"])
+        mock_run.assert_has_calls(
+            [
+                mock.call(["mountpoint", "/target"]),
+                mock.call(["zpool", "export", "-a"]),
+            ]
+        )
+        self.assertEqual(2, mock_run.call_count)
 
     async def test_examine_systems(self):
         # In LP: #2037723 and other similar reports, the user selects the