support vcloud in micro-stemcell and director

Change-Id: Ie05a6af6a65db48f4c49b4a2f8871ce19944b931
fix system parameters for bosh agent

For bosh agent, we should always use vsphere as infrastructure when building
for vcloud.

Change-Id: Iec160d032350cedca766bb2e9bfc03a345b6726d