Synchronization vmexit of all vcpus

When vm boots to login, use ./record_ctrl enable and kvm will trap
all vcpus simultaneously. The first trapped vcpu is named MASTER,
and will send IPI to all other vcpus to trap, then release together.

NOTICE: DO NOT enable record at boot time!!!! Only one vcpu is enabled
at boot time and IPI will fail to response.

Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>