AliasRegistry / ServiceRegistry not cleared for pure commonjs tests

[thecapdan]

We have a line in JsTestDriver runner.js to clear the AliasRegistry and ServiceRegistry at the end of each test:

if(typeof(br) != "undefined")        
{
            if(br.AliasRegistry && br.AliasRegistry.clear) {
                br.AliasRegistry.clear();
            }
            if(br.ServiceRegistry && br.ServiceRegistry.clear) {    
            br.ServiceRegistry.clear();
            }

When we have tests running against common js only code, br will be undefined and the Regitries will not be cleared. We will need to require them for such cases.