Code review comment for lp:~kaihuan-pkh/cloud-init/cloud-init

Hi, Scott :
I signed the contributors agreement.
the previous merging request (284627)  is just add one file ( cloudinit/sources/DataSourceAliYun.py )，which we copied from ec2 datasource and change the DEF_MD_URL to our testing environment.
from the day i push that commit to now, we have more changes on cloud-init （but have not yet push to launchpad site for now ) , the main changes including:
1.  add some new config modules in cloudinit/config/2.  add some distro support in cloudinit/distros/3.  change the aliyun datasource DEF_MD_URL again4.  some bug fix
now, our local devel branch is almostly complete, and we are in process of testing.  we will push a new merge request in later when it passed test.
by the way, we are design cloud-init self-upgrade plan, do you have some suggest ?
thx.