Make tests which first provide a negative assertion via 'not', then

Make tests which first provide a negative assertion via 'not', then
a pipeline, and then a positive assertion via grep, use two RUN lines
instead.

Supporting these complex ideas of 'success' and 'failure' across
multiple stages of a pipeline is brittle in the shell world, and would
block switching to ShTest format; it only worked due to contrivances
introduced by the TclTest format.

Writing this as two separate RUN lines seems clearer in any event.

This is another step toward completely removing TclTests from lit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159524 91177308-0d34-0410-b5e6-96231b3b80d8