btrfs: test device delete with EIO on src dev

btrfs: test device delete with EIO on src dev

This test case tests if the device delete works with
the failed (EIO) source device. EIO errors are achieved
usign the DM device.

This test would need following btrfs-progs and btrfs
kernel patch
   btrfs-progs: device delete to accept devid
   Btrfs: device delete by devid

However when btrfs-progs patch is not found this test will
not run, and when kernel patch is not found btrfs-progs
will fail gracefully and thus the test script.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>