[BUG] Update Firmware via `redfish/v1/UpdateService/update` Endpoint

[davidallendj]

Problem

Currently, magellan is capable of updating firmware using the /redfish/v1/UpdateService/SimpleUpdate endpoint via the gofish library. However, in reference to #71 and a simple fix provided in the comments, I think it is reasonable to try and incorporate firmware updates via the /redfish/v1/UpdateService/update endpoint as well especially since this the endpoint used with OpenBMC as mentioned in #71.

Possible Solution

It would probably make more sense to solve this issue upstream in the gofish library instead of magellan directly. However, given that there is already a temporary provided solution, it may be possible to use the temporary solution until the necessary changes are made to gofish.

Definition of Done

This issue is complete when firmware updates can be performed that require the /redfish/v1/UpdateService/update endpoint instead of the /redfish/v1/UpdateService/SimpleUpdate endpoint.

Other Context

I made a comment on #385 that may be related.