Only attempt to load a single name in reservation checking

[gbrodman]

We don't need to load the whole list if we're only checking one name during something like a domain create.

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This change is 

[CydeWeys]

This might reduce performance? The current behavior is that the reserved list is loaded from the DB and then cached for an hour. (Reserved lists aren't that large, so loading them in their entirety and caching them is doable.)

This changes it to always loading every single entry in a reserved list individually, and not caching them?

[gbrodman]

eh yeah that's why i didn't submit it for review yet, i was musing on making sure the cache works in the original version and seeing if this could still involve caching

[gbrodman]

eh yeah once per hour loading the whole thing is probably fine