Fix issue reported by Godmar Back:

    I may have found a problem with the triple fault patch, though I don't
    know how to solve it.
    If you add a *(int *)0=42 right after paging_init(), but before
    intr_init(), gdb will just hang:

...

    where it hangs while Pintos prints:

    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    Triple fault: stopping for gdb
    etc.

    It stops properly if I don't next-step (that is, if I just let it run.)