[Lilee.CentOs] Change base image to official centos 6
[Lilee.CentOs] Generate SSH host key at the begin
[Lilee.CentOs] Fix yum-config-manager
[Lilee.CentOs] Add yum update before downgrade
[Lilee.CentOs] Set toolchain path to /home/startrek
[Lilee.CentOs] Copy repo to /usr/local/bin
[Lilee.CentOs] Move yum update downgrad later
[Lilee.CentOs] Add some comments