Add tests for CAN and diag JSON payloads without 0x prefix.
Add tests for CAN and diag JSON payloads without 0x prefix.

Fixed https://github.com/openxc/openxc-android/issues/163

ene-ilies/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,mgiannikouris/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware