Update pulse config to use Ubuntu 14.04 instead of 12.04 (#453)

Simple PR to replace the Ubuntu nodes in use for pulse triggered tests from 12.04 to 14.04. @andreeamatei or @andreieftimie could one of you have a quick look over it?
My fault. Before we had 21.0 and 22.0. But I don't see why we need two entries here. So I updated it accordingly.

Does it look fine now?