fuse: write inode in fuse_release()

A race between write(2) and close(2) allows pages to be dirtied after
fuse_flush -> write_inode_now().  If these pages are not flushed from
fuse_release(), then there might not be a writable open file later.  So any
remaining dirty pages must be written back before the file is released.

This is a partial revert of the blamed commit.

Reported-by:  <syzbot+6e1efbd8efaaa6860e91@syzkaller.appspotmail.com>
Fixes: 36ea2337

 ("fuse: write inode in fuse_vma_close() instead of fuse_release()")
Cc: <stable@vger.kernel.org> # v5.16
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>