behavior as file systems that use the monolithic /sbin/mount command.
See the MS_NOMTAB macro in utils-linux-ng/mount/mount.c.
Note that mount(8) has MS_USERS and MS_USER in the "nomtab" category
as well, but mount.nfs needs to record those values so that unmounting
a user-mounted NFS file system can work.
While we're here, fix some white space damage in fix_opts_string().