ANDROID: x86_64_cuttlefish_defconfig: Disable KPTI

Disable page table isolation to avoid kernel panics when booting kernels
under KVM. Temporary workaround while this issue is investigated.

Bug: 78252157
Bug: 71362031
Change-Id: I5ba126b08678fcb8fd7bc31fe79de80fa81cf869
Signed-off-by: Greg Hartman <ghartman@google.com>
Signed-off-by: Alistair Strachan <astrachan@google.com>