Read agent settings from vmdk instead of cdrom iso to enable SRM on vsphere

Enable SRM on vsphere by replacing the workflow of reading settings from cdrom with reading from attached independent disk:
We create a vmdk template file and it contains the env file which is stuffed with spaces and the total size of string content is fixed, which is 1MB. In vsphere cpi, we replace the string content with specific environment setting JSON string and maintain the total size of 1MB. This way we create a new vmdk file based on vmdk template file. Then use the created vmdk file to upload and attach to VM as independent disk.