Add a missing switch to support for CentOS 7.0
Add a missing switch to support for CentOS 7.0

In base role, only CODENAME_MAJOR=6 is actually use, this change enable
CentOS 7.0 to be built without the following error:
"Cannot find a valid baseurl for repo: base/$releasever/x86_64"

lebauce/edeploy,enovance/edeploy,redhat-cip/edeploy,enovance/edeploy,redhat-cip/edeploy,lebauce/edeploy,enovance/edeploy,redhat-cip/edeploy,redhat-cip/edeploy,lebauce/edeploy,enovance/edeploy,lebauce/edeploy