Make the clang-analyzer job fail when lint is introduced

We run clang's scan-build tool in a Jenkins job called wiredtiger-clang-analyzer, but currently it gets little attention because it never fails.

We should review the current failures and eliminate as many as we can. Then we should set a threshold so that if new warnings are introduced the job fails. Ideally we would review that and reduce the threshold when the number of warnings goes down.