Cleaned up function signatures to fix compile errors

[nebrius]

This PR changes the function signatures in the derived AMQP class to more accurately match the signatures of the methods that it overrides.

Note: this is a type signature change only, this does not change the compiled output AFAICT.

Checklist

• I have read the [contribution guidelines] (https://github.com/Azure/azure-iot-sdk-node/blob/master/.github/CONTRIBUTING.md).
• I added or modified the existing tests to cover the change (we do not allow our test coverage to go down).
• If this is a modification that impacts the behavior of a public API
  • I edited the corresponding document in the devdoc folder and added or modified requirements.

Reference/Link to the issue solved with this PR (if any)

#119

Description of the problem

There are some inconsistencies in one of the derived classes in this module that causes it to not compile in some apps using this module. For more details, please see #119

Description of the solution

This approach fixes the problem by updating the signatures of the overridden methods in the Amqp class to match those in the Client.Transport class.