qcow2: Add refcount_bits to format-specific info

qcow2: Add refcount_bits to format-specific info

Add the bit width of every refcount entry to the format-specific
information.

In contrast to lazy_refcounts and the corrupt flag, this should be
always emitted, even for compat=0.10 although it does not support any
refcount width other than 16 bits. This is because if a boolean is
optional, one normally assumes it to be false when omitted; but if an
integer is not specified, it is rather difficult to guess its value.

This new field breaks some test outputs, fix them.

Signed-off-by: Max Reitz <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>