test: bp fix for test-http-get-pipeline-problem.js
backport fix for test-http-get-pipeline-problem.js from master to 0.12.X. We've been seeing an intermittent failure in runs for zLinux with SLES 12. We confirmed that this fix resolves the issue so would like it in 0.12.X
The original commit does not apply cleanly as the paths were changed, but the actual change is identical. The original commit was:
https://github.com/nodejs/node/commit/3ba4f71fc4a1b3acdcaaa250bc5ba81442257e09