Clarify when to use cache (or not) when loading premium lists

You don't want to use the cache when loading them for the purposes of updating
them, but you definitely do still want to use the cache when checking the
price of individual domains.

In [] the cache clearing of premium lists on update was removed. This
is a good thing in aggregate because the cache is per-instance and thus
misleading, but it also caused us to not be able to update the same premium
list twice within an hour because the second update would hit a "PremiumList
was concurrently edited" exception, owing to first loading the stale version
from the cache for the purposes of updating it. Now we bypass the cache for
that purpose.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=197768142

java/google/registry/tools/CreateOrUpdateTldCommand.java

@@ -362,8 +362,9 @@ abstract class CreateOrUpdateTldCommand extends MutatingCommand {
 
       if (premiumListName != null) {
         if (premiumListName.isPresent()) {
-          Optional<PremiumList> premiumList = PremiumList.get(premiumListName.get());
-          checkArgument(premiumList.isPresent(),
+          Optional<PremiumList> premiumList = PremiumList.getUncached(premiumListName.get());
+          checkArgument(
+              premiumList.isPresent(),
               String.format("The premium list '%s' doesn't exist", premiumListName.get()));
           builder.setPremiumList(premiumList.get());
         } else {