vars were not being processed for imported tests

[netjunki]

When trying to make use of the --vars option in my tests I discovered it wasn't being passed from the cli into the imported test files. This should fix that. This let's me play this trick with running my tests:

pyresttest https:// testall.yaml --vars="{'domain':'example.com'}"
In suite1.yaml (which is imported in testall.yaml)
  - url: {template: "api.$domain/test"}

Since I have dozens of test environments but I need to be able to execute the same test suite against all of them.