Bus 1 transceiver is kept active while car is off

[sshane]

We only use bus 0/transceiver 1/3 for CAN ignition, so bus 1/transceiver 2 is kept up needlessly. The power save mode is set correctly, but setting the safety mode to SILENT or NOOUTPUT calls set_can_mode which disables and re-enables transceivers 2 and 4 to configure them without checking the power save mode.

Do we care about this? We may want to use bus 1 in the future while the car is off, but right now we don't.