Re-land removing RECOVERY_AS_BOOT check for init_first_stage

This has kept adb_debug.prop from being installed for
legacy devices with BOARD_USES_RECOVERY_AS_BOOT set to
true.

Bug: 192432810
Bug: 193291885
Test: `lunch aosp_flame-userdebug` and checks `get_build_var
      BOARD_USES_RECOVERY_AS_BOOT` is true.
Test: `make bootimage_debug` then checks
      $OUT/debug_ramdisk/adb_debug.prop exists
Test: build/soong/build_test.bash --dist --incremental

Change-Id: I28e2c082512791407167b610843f18731ed6d673