Remove reliance on `out`'s value.

[danbugs]

We should modify the Abort and DebugPrint OutBActions to no longer rely on the value from out. Particularly, we should only rely on out to cause a VM exit and not on specifics of the mechanism. This will be helpful for the future when we add support other architectures that may not have out (e.g., ARM) and we need to change our doorbell mechanism. An alternate implementation for Abort and DebugPrint would be to pass a Hypervisor to the outb handler and retrieve registers values from the guest with info, which should be easy to do once #312 is merged.

Note: We should also change the naming from outb to out.