5.2.0.0 broke support for older iLO5 upgrades in flashfwpkg

[moonrail]

On older iLO5 versions the following error is raised on upgrading the iLO firmware via ilorest flashfwpkg:

ilorest rc 255: ERROR: 'Accept3rdPartyFirmware'

This is - again - a KeyError due to directly accessing the key in the response of the redfish API:
https://github.com/HewlettPackard/python-redfish-utility/blame/v5.2.0.0/src/extensions/iLO_REPOSITORY_COMMANDS/FwpkgCommand.py#L122

Apparently the older iLO5 firmware does not return the key Accept3rdPartyFirmware.

Due to this breaking change, we are unable to upgrade the an old iLO5 to a new and up to date firmware which supports this feature and returns this key.

This is also present in 5.3.0.0, as this line of code is the same.