kernel: not all vnode ops should default to ENOSYS

kernel: not all vnode ops should default to ENOSYS

Some vnode op dispatch functions need to call generic implementations or
return a value different than ENOSYS.  They are:

- vop_setfl needs to return 0
- vop_rwlock needs to return -1
- vop_rwunlock needs to be a no-op
- vop_cmp needs to compare vnode pointers
- vop_frlock needs to call fs_frlock()
- vop_poll needs to call fs_poll()
- vop_pathconf needs to call fs_pathconf()
- vop_dispose needs to call fs_dispose()
- vop_getsecattr needs to call fs_fab_acl()
- vop_shrlock needs to call fs_shrlock()
- vop_vnevent needs to return ENOTSUP