Update docker images
Update docker images

This change updates docker images for CentOS 6 and ubuntu 14.04 ARM.
It also replaces RHEL 7 docker image with CentOS 7 one.
The images now contain clang 3.9 with PGO support

crummel/dotnet_core-setup,rakeshsinghranchi/core-setup,chcosta/core-setup,chcosta/core-setup,ericstj/core-setup,ericstj/core-setup,MichaelSimons/core-setup,steveharter/core-setup,chcosta/core-setup,ericstj/core-setup,crummel/dotnet_core-setup,wtgodbe/core-setup,rakeshsinghranchi/core-setup,MichaelSimons/core-setup,weshaggard/core-setup,wtgodbe/core-setup,zamont/core-setup,zamont/core-setup,ericstj/core-setup,crummel/dotnet_core-setup,steveharter/core-setup,chcosta/core-setup,rakeshsinghranchi/core-setup,zamont/core-setup,zamont/core-setup,weshaggard/core-setup,MichaelSimons/core-setup,steveharter/core-setup,zamont/core-setup,crummel/dotnet_core-setup,chcosta/core-setup,steveharter/core-setup,weshaggard/core-setup,rakeshsinghranchi/core-setup,rakeshsinghranchi/core-setup,MichaelSimons/core-setup,ericstj/core-setup,ericstj/core-setup,crummel/dotnet_core-setup,chcosta/core-setup,wtgodbe/core-setup,crummel/dotnet_core-setup,steveharter/core-setup,weshaggard/core-setup,weshaggard/core-setup,MichaelSimons/core-setup,wtgodbe/core-setup,MichaelSimons/core-setup,rakeshsinghranchi/core-setup,wtgodbe/core-setup,zamont/core-setup,weshaggard/core-setup,steveharter/core-setup,wtgodbe/core-setup