KVM: selftests: Explicitly clobber the IDT in the "delete memslot" testcase

Explicitly clobber the guest IDT in the "delete memslot" test, which
expects the deleted memslot to result in either a KVM emulation error, or
a triple fault shutdown.  A future change to the core selftests library
will configuring the guest IDT and exception handlers by default, i.e.
will install a guest #PF handler and put the guest into an infinite #NPF
loop (the guest hits a !PRESENT SPTE when trying to vector a #PF, and KVM
reinjects the #PF without fixing the #NPF, because there is no memslot).

Note, it's not clear whether or not KVM's behavior is reasonable in this
case, e.g. arguably KVM should try (and fail) to emulate in response to
the #NPF.  But barring a goofy/broken userspace, this scenario will likely
never happen in practice.  Punt the KVM investigation to the future.

Link: https://lore.kernel.org/r/20240314232637.2538648-8-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>