btrfs-progs: receive: restore capabilities after chown

btrfs-progs: receive: restore capabilities after chown

Capabilities are cleared after chown, and the btrfs-stream encodes the
CHOWN command after any SET_XATTR command. So the capabilites are not
always preserved.

This could be fixed in kernel to emit the instructions in the right
order, but fix in userspace will make it work for older kernels.

If we see the capabilities among xattrs, cache the value and apply it
again in case it's followed by chown on that file.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=68891
Reported-by: Juan Orti Alcaine <j.orti.alcaine@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>