ART: Temporarily move 3 checker tests away from D8

Postpones switching to D8 for tests failing on the ART buildbots.

All of the tests modified were failing on 64-bit ARM. Only
551-checker-shifter-operand was failing on 32-bit ARM.

Bug: 65168732
Test: art/test.py --target -j4 -r --64 -t 551-checker-shifter-operand
Test: art/test.py --target -j4 -r --64 -t 626-checker-arm64-scratch-register
Test: art/test.py --target -j4 -r --64 -t 706-checker-scheduler

Change-Id: Ie02d8dc46a36ebe5ddb9a6e24e96bc2bdc4f97c7