Fix TestDaemonNoSpaceLeftOnDeviceError

This test is testing if any "no space left on device" errors
that occur during `docker pull` will not be masked by other
errors. To test for this, a new loopback-device was created,
and used as `--data-dir` ("/var/lib/docker").

However, `/var/lib/docker` is used for storing various
other things, including a `cache.db` database, used by
BuildKit, which is created during startup of the daemon.
Creation of that file failed (due to `--data-dir` path
being on a mount with limited size), which caused daemon
start to fail before the test was able to run.

This patch changes the size-limited mount to be used for
the storage-driver directory only, so that the test is
not affected by other parts of the code attempting to
write files in it.

To have a predictable path; the daemon used in this test
is configured to use the `vfs` storage-driver.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

integration-cli/docker_cli_daemon_test.go

@@ -1811,10 +1811,10 @@ func (s *DockerDaemonSuite) TestDaemonNoSpaceLeftOnDeviceError(c *check.C) {
 	dockerCmd(c, "run", "--rm", "-v", testDir+":/test", "busybox", "sh", "-c", "dd of=/test/testfs.img bs=1M seek=3 count=0")
 	icmd.RunCommand("mkfs.ext4", "-F", filepath.Join(testDir, "testfs.img")).Assert(c, icmd.Success)
 
-	dockerCmd(c, "run", "--privileged", "--rm", "-v", testDir+":/test:shared", "busybox", "sh", "-c", "mkdir -p /test/test-mount && mount -n /test/testfs.img /test/test-mount")
+	dockerCmd(c, "run", "--privileged", "--rm", "-v", testDir+":/test:shared", "busybox", "sh", "-c", "mkdir -p /test/test-mount/vfs && mount -n /test/testfs.img /test/test-mount/vfs")
 	defer mount.Unmount(filepath.Join(testDir, "test-mount"))
 
-	s.d.Start(c, "--data-root", filepath.Join(testDir, "test-mount"))
+	s.d.Start(c, "--storage-driver", "vfs", "--data-root", filepath.Join(testDir, "test-mount"))
 	defer s.d.Stop(c)
 
 	// pull a repository large enough to overfill the mounted filesystem