btrfs-progs: corrupt-block: Change -I flag parameter format

btrfs-progs: corrupt-block: Change -I flag parameter format

Presently, if we want to corrupt a particular item we need to call
corrupt block like so:

btrfs-corrupt-block -I -K <objectid,type,offset> -r "numeric rootid"

This is problematic because the -K option not only sets the key to the
item that the -I option should corrupt but it also signals that we
want to corrupt the key itself. This way we cannot really use the
program with the following semantics:

"Corrupt only the item which corresponds to this key but leave the
key intact"

This patch aims to fix this by changing the format of the -I flag. So
if one wants to corrupt only an item (and leave the key intact) they
should use:

  btrfs-corrupt-block -r <numeric rootid> -I <objectid,type,offset>

In addition to this problem, -K doesn't really understand the the "-r"
argument, so when using it in conjunction with -I to corrupt an item,
not part of the root tree, it will always produce an error:

  Couldn't find the key to corrupt

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>