Factor out specification of omnibus distributions.
Build ununtu-14.04 omnibus package.
Merge pull request #40 from ClusterHQ/ubuntu-omnibus

[FLOC-1069] Ubuntu omnibus
Add centos builder.
Add centos omnibus builder.
Bypass trial args in buildbot.
Merge branches 'centos-builder-FLOC-1024' and 'vagrant-test' into staging