block: refresh bs->total_sectors on reopen

After reopening a BlockDriverState, it's possible that the size of the
underlying file has changed.  This for example is covered by test 171.

Right now, this is handled by the raw driver's has_variable_length = true
setting.  Since this will be removed by the next patch, handle it on
reopen instead, together with the existing bdrv_refresh_limits.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230407153303.391121-4-pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>