
Currently tgz images are supported only when the names of VHD files within follow the format of "0.vhd, 1.vhd, ... (n-1).vhd" called VDI chain. To maximize the range of support, the arbitrary named VHD file could be renamed to 0.vhd when the tgz image only has a single VHD file. Change-Id: I01cadf26262b20f1ad5a19e4441b42a0155f5a52