Revert "Adding main.repo to CentOS6 Dockerfile"

This reverts commit ee3b171fd2ab87052469b208c34355d1562a9987.
Revert "Creating main repo for CentOS Dockerfiles"

This reverts commit 1ff5095eee1fefb792f90f35c50ae2ad2d5ea0ac.
Revert "Updating CentOS5 Dockerfile"

This reverts commit bca04a689190d7c8cafa336969c717efd520780f.
Revert "Creating main repo for CentOS Dockerfiles"

This reverts commit 45a329bb9acd7ec87d83a8c184b8fa1bcfbfa852.