qcow2: Prepare qcow2_update_snapshot_refcount() for adding L2 slice support

qcow2: Prepare qcow2_update_snapshot_refcount() for adding L2 slice support

Adding support for L2 slices to qcow2_update_snapshot_refcount() needs
(among other things) an extra loop that iterates over all slices of
each L2 table.

Putting all changes in one patch would make it hard to read because
all semantic changes would be mixed with pure indentation changes.

To make things easier this patch simply creates a new block and
changes the indentation of all lines of code inside it. Thus, all
modifications in this patch are cosmetic. There are no semantic
changes and no variables are renamed yet. The next patch will take
care of that.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 8ffaa5e55bd51121f80e498f4045b64902a94293.1517840877.git.berto@igalia.com
Signed-off-by: Max Reitz <mreitz@redhat.com>