Fix patchoat_test for heap poisoning

The test was disabled for heap poisoning; keep it disabled.

The TEST_DISABLED_FOR_HEAP_POISONING macro is in fact just
a conditional return, and I didn't account for it properly.

Bug: 109677607
Test: test-art-host-gtest-patchoat_test ART_HEAP_POISONING=true
Change-Id: I40266d0a06102e4d8bc52357b884b0e7d9fd2630