set imageType in VMWare_VCloud_SDK_Vdc::uploadMedia

`VMware_VCloud_SDK_Vdc::uploadIsoMedia` and `VMware_VCloud_SDK_Vdc::uploadFloppyMedia` both delegate to the private method `VMware_VCloud_SDK_Vdc::uploadMedia`. However `VMware_VCloud_SDK_Vdc::uploadMedia` never makes use of the defined `$imageType` variable.