Initialize waiting_for_message field of struct vcpu.
Initialize waiting_for_message field of struct vcpu.

Bug: 131434148
Change-Id: I28364bd8463f6b16980d865c305e35122af9a8d5

project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification,project-oak/hafnium-verification