virStorageFileGetMetadata does not report error if we can't interrogate
the file somehow. Clarify this in the description of the @report_broken
flag as it implies we should report an error in that case. The problem
is that we don't know whether there's a problem and unfortunately just
offload it to qemu.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>