fix parameter passing in Cloudsearch Layer2 -> Layer1 -> AWSAuthConnection

This fix issue #1629
The parameters passing from Layer 2 to Layer 1 constructor are misaligned; host is before port in Layer 1 but not in Layer 2. In fact, let's avoid accidental positional problem all together by fully qualifying the parameter names. 

Things to verify: 
- is Layer 2's session_token supposed to be Layer 1's security_token?
- Is AWSAuthConnection's host supposed to be Layer 1's region.endpoint?