Entitlement Preferences should be just preference

[mtgibbs]

There are situations where a user has an entitlement that is only valid for a Single Scan or only a Subscription. In the situation where the user's chosen entitlement is not valid, it should default to the given one regardless of the preference selection. Currently, the preference is acting as a fixed value, so it can't fall back to the other option and halts the scan.

Included in this issue is that the failure simply says that the Assessment Type and Entitlement was not found, which is hard for the user to understand why they couldn't run a scan that was just configured.