[DEV] Add Redfish API tests for more predictable behavior on different hardware

[davidallendj]

Short Description
After using Magellan with different systems with different Redfish versions and implementations, it has become apparent that Magellan needs a way of ensuring predictable behavior. This is especially needed when testing on new systems where it would easier to see when and where there is a failure.

For example, one system may provide EthernetInterfaces under the /redfish/v1/Systems/EthernetInterfaces endpoint while another system provides it via the /redfish/v1/Managers/EthernetInterfaces endpoint. This real scenario required handling each endpoint differently, and would be able to be added and caught by tests if the tool is ran on other hardware with a similar Redfish API.

Definition of Done
This issue is considered completed once there are tests for testing Redfish's API to provide some guarantees. These tests can simply be HTTP requests that assert specific output and does not require any other sophisticated features.

Additional context
This issue is related to #31, but strictly addresses adding unit tests for Redfish API predictability.