Freeze docker base image to use ubuntu 14.04
Freeze docker base image to use ubuntu 14.04

The phusion:baseimage has changed to ubuntu 16:04 even though the doc on
docker hub says otherwise. This breaks our build and the develop
environment.

plamut/ggrc-core,j0gurt/ggrc-core,edofic/ggrc-core,edofic/ggrc-core,AleksNeStu/ggrc-core,andrei-karalionak/ggrc-core,andrei-karalionak/ggrc-core,edofic/ggrc-core,andrei-karalionak/ggrc-core,AleksNeStu/ggrc-core,AleksNeStu/ggrc-core,selahssea/ggrc-core,josthkko/ggrc-core,andrei-karalionak/ggrc-core,plamut/ggrc-core,kr41/ggrc-core,selahssea/ggrc-core,VinnieJohns/ggrc-core,VinnieJohns/ggrc-core,josthkko/ggrc-core,j0gurt/ggrc-core,josthkko/ggrc-core,j0gurt/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,kr41/ggrc-core,j0gurt/ggrc-core,kr41/ggrc-core,edofic/ggrc-core,VinnieJohns/ggrc-core,selahssea/ggrc-core,AleksNeStu/ggrc-core,VinnieJohns/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,kr41/ggrc-core