Fallback to ubuntu 12.04 for circle builds.
Fallback to ubuntu 12.04 for circle builds.

dmlond/aact,tibbs001/aact-1,ctti-clinicaltrials/aact,tibbs001/aact-1,ctti-clinicaltrials/aact,tibbs001/aact-1,dmlond/aact,dmlond/aact,dmlond/aact,ctti-clinicaltrials/aact