BounceToKernel will make vCPU quit from guest ring3 to guest ring0, but
vCPUWaiter is not cleared when we unlock the vCPU, when next time this vCPU
enter guest mode ring3, vCPU may enter guest mode with vCPUWaiter bit setted,
this will cause the following BounceToKernel to this vCPU hangs at
waitUntilNot.
Halt may workaroud this issue, because halt process will reset vCPU status into
vCPUUser, and notify all waiter for vCPU state change, but if there is no
exception or syscall in this period, BounceToKernel will hang at waitUntilNot.
PiperOrigin-RevId: 256299660
85b27a9f8f