udf: convert novrs to an option flag

There's no reason to treat novers specially, convert it
to a flag in uopt->flags like other flag options.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <b5d53492-b99a-4b3c-82c0-581df9a9e384@redhat.com>