unittest: Disable MachineInstrClone.CopyCallSiteInfo entirely

Somehow, details about the host architecture are creeping into the bogus
target set up in MFCommon.inc, causing call site info to be disabled:

http://lab.llvm.org:8011/builders/lld-x86_64-win7/builds/41476
http://lab.llvm.org:8011/builders/clang-s390x-linux-lnt/builds/17987

Disable the test to unblock the bots until I can figure this out.