Fix art::ArchTest::FinalizeSetup not being called.

CommonRuntimeTestImpl::SetUp() is calling FinalizeSetup. Since
CommonRuntimeTestImpl::FinalizeSetup is not virtual (it's virtual
one step higher in class hierarchy in CommonRuntimeTestBase), overridden
version in ArchTest was never used. This is causing ArchTest to
fail with openjdk8u60 version of java.lang.reflect (it's calling
Class#getDeclaredField in clinit, which fails on 32 bit
version because of different pointer sizes [arch_test forces
64-bit ISA])

Bug: 28666126
Test:  make -j 32 test-art-host-gtest
Change-Id: Ief370f5b18ef787575ac0f88ecbe17ebbf037542