pid_ns: Make pid_max per namespace

euler inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8TCPY



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The adjusted pid_max on the host also takes effect in the container.
Move pid_max to pid_namespace to fix this problem.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Yi Yang <yiyang13@huawei.com>