Follow-up for r324429: "[LCSSAVerification] Run verification only when asserts are enabled."

Before r324429 we essentially didn't have a verification of LCSSA, so
no wonder that it has been broken: currently loop-sink breaks it (the
attached test illustrates the failure).

It was detected during a stage2 RA build, so to unbreak it I'm disabling
the check for now.

llvm-svn: 324445