Fix state on blocking mailbox_receive.
Fix state on blocking mailbox_receive.

State was being set to vcpu_state_blocked_interrupt by
api_wait_for_interrupt. It should remain vcpu_state_blocked_mailbox.

Change-Id: I9289f93fdf4c674a701b79b21bb53f29385237b0

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