[BasicAA] Temporarily disable two tests

These tests are breaking three independent upstream buildbots (as well
downstream ones). These breakages have appeared mysteriously,
consistently, and during different revisions. Sadly, none of
{ASAN,TSAN,MSAN,UBSAN} flag anything, so the cause here is nonobvious.

Until we've figured this out, it seems best to disable these tests
entirely, so that the affected bots don't remain silent about any other,
unrelated failures.

Please see PR42719 for more information.

llvm-svn: 366986