Extend test to create the network

[lvirbalas]

Right now we have an orgvdcnetwork_test.go, which tests only finding of the network. However, the library actually has functionality to create Org vDC networks right now. This can be tested by using Terraform vCD provider.

The test needs to be extended to actually create the network and then find the one that has been created.

After this change the following parameter in the tests' config.yaml should not require an existing network, rather it should depict how to name the network that will be created by tests or, if possible, we can drop it all-together and make configuration simpler: network: TerraformNetwork