fix #29564148

Global swapout can happen even with swappiness set to 0. In some
scenario, we do want OOM instead of unexpected global swapout.

This extends value range of vm_swappiness, and disables swapout
completely by setting swappiness to -1.
Signed-off-by: NXu Yu <xuyu@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>