[LTP] [RFC] ltp test add reboot function

[Cixi Geng]

Hi ALL:

I want to add a reboot function in LTP for my team write a memory page
related case，
and need reboot to make the memory cache or some likely it pure clear.

So I want to add a tst_needs_reboot. when it was set, reboot the
machine and continue
run test from the point before.

I think  this requirement is meaningful， So can you give me some advise?