quota: Update documentation
quota: Update documentation

Mention that quota netlink messages are sent only in initial network
namespace.

Signed-off-by: Jan Kara <596727c8a0ea4db3ba2ceceedccbacd3d7b371b8@suse.cz>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs