系统挂起，显示 "systemd-journald[xx]:Received SIGTERM from PID 1 (systemd)"

Issue

• 在切换 root 后系统挂起，如下所示

  [  OK  ] Reached target Switch Root.
  [  OK  ] Started Plymouth switch root service.
      Starting Switch Root...
  [   4.918903] systemd-journald[xx]: Received SIGTERM from PID 1 (systemd)
  

• 启动一个较旧的内核无法解决这个问题

• 配置串行控制台时，串行控制台会显示以下堆栈追踪信息（时间戳可能会不同）

  [    4.948513] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
  [    4.948513] 
  [    4.952201] CPU: 0 PID: 1 Comm: systemd Not tainted 3.10.0-957.5.1.el7.x86_64 #1
  [    4.955057] Hardware name: XXX
  [    4.957592] Call Trace:
  [    4.958917]  [<ffffffffa6361e41>] dump_stack+0x19/0x1b
  [    4.961080]  [<ffffffffa635b550>] panic+0xe8/0x21f
  [    4.963215]  [<ffffffffa5c9e406>] do_exit+0xa36/0xa40
  [    4.965744]  [<ffffffffa5c9e48f>] do_group_exit+0x3f/0xa0
  [    4.968339]  [<ffffffffa5c9e504>] SyS_exit_group+0x14/0x20
  [    4.971171]  [<ffffffffa6374ddb>] system_call_fastpath+0x22/0x27