destroy_cloud_config_vdi_after_boot deletes the cloud config VDI too soon

[wkleinhenz]

Currently Im using cloud config files to bootstrap a VM Image created using packer. this is mainly being used to set host specific things like the network configuration and host name. when using
destroy_cloud_config_vdi_after_boot = true, the expected_ip_cidr setting and the default power_state setting which i believe is Running the cloud config VDI is deleted as soon as it meets the running state, but this means that the VM isn't able to access the cloud config files.

Proposed changes:

• have the provider wait a configurable number of seconds before deleting the cloud config VDI after it reaches the running state
• have the provider wait a configurable number of seconds before deleting the cloud config VDI after the expected_ip_cidr returns that the VM is ready