fusefs: Upgrade FUSE protocol to version 7.33.

This commit upgrades the FUSE API to protocol 7.33,
it doesn't implement any of protocol 7.33's new features,
setxattr is tested for binary compatibility with protocol version 7.32.

Update sys/fs/fuse/fuse_vnops.c

Reviewed by: Alan Somers <asomers@FreeBSD.org>
Pull Request: https://github.com/freebsd/freebsd-src/pull/1681