Well this is a bit frustrating. After having finished up reviews on a few other devices I have finally been able to use my Nexus 6P as a daily driver device. Of course the first thing I decided to do was unlock the bootloader, flash recovery, and root the device. Now I am stuck with the warning letting me know that my device has an unlocked bootloader and can't be checked for corruption. It isn't the end of the world, but is a huge annoyance.
It turns out that this message is built into the bootloader. There is no mod you can flash to get rid of it. You can get rid of the same message on the Nexus 6 by flashing a custom kernel since the warning is built into the kernel on that device. The only way to get rid of this warning on the Nexus 6P is to re-lock your bootloader. In the end it only adds a few seconds to your boot up experience. Maybe someone will come up with a way to get rid of this warning soon.