init: reboot to bootloader on crash for development builds

Currently, if init crashes, the kernel panics.  During development, we
would like to catch this crash before the kernel panics and reboot
into bootloader. This will prevent boot looping bad configurations,
particularly desired in test labs where manual intervention would
otherwise be required to reset the devices.

Keep the existing behavior for user builds, as init crashes should be
rare for production builds and rebooting the device is the correct
behavior for end users.

Bug: 34147472
Test: Boot bullhead userdebug, force init to crash, check that the
      device is in bootloader
Test: Boot bullhead user, force init to crash, check that the kernel
      panics and the device reboots as it did previously
Change-Id: Iab3d45ed0d1f82ffaad2a0835d9ca537c0516421