Fix bug: test/Regression/Transforms/InstCombine/2002-05-14-TouchDeletedInst.ll

"This testcase caused instcombine to fail because it got the same instruction on
it's worklist more than once (which is ok), but then deleted the instruction.
Since the inst stayed on the worklist, as soon as it came back up to be
processed, bad things happened, and opt asserted."

llvm-svn: 2623