Build the ROS image in Aliyun

[niusmallnan]

Aliyun support KVM virtualization, support two image formats: raw and vhd.

Import Customized Linux: https://help.aliyun.com/document_detail/48226.html

To do list:

1. Build an image by os-packer(type: qemu), test whether this image will work.
2. Support Aliyun Datasource in RancherOS cloud-init.
3. Maybe need to modify the file system (from overlay to ext)

[kingsd041]

I can import the image on Aliyun and use it to start the instance. Checked the cpu, memory, disk, hostname and other information, and some manual tests on the ros command.
I think rancheros v1.1.2-rc2 works fine on Aliyun.

I found an issue about disk resize.
link：#2186