Rewrite testBadApkOnly_Phase3 (1/n)

1. Wait for 120s for reboot to happen. This improve the stablity of
   virtual devices which sometimes could be slow in shutdown.
2. Use assertThrows to catch exception when reboot doesn't happen which
   gives us better error messages than expecting next phase to fail.

Bug: 143999213
Test: atest StagedRollbackTest#testBadApkOnly
Change-Id: Ibafcbe7e003fb92991d6f8fe2fde7b344ffd6db6