recovery: turn on text display for install errors in debug builds

Hopefully this will reduce the number of OTA "bugs" reported that are
really just someone having changed their system partition,
invalidating future incremental OTAs.

Also fixes a longstanding TODO about putting LOGE() output in the
on-screen display.

Change-Id: I44e5be65b2dee7ebce2cce28ccd920dc3d6e522e