SSP-2818 Fix EA reminder suppression by sorting List not Set

Can't use TreeSet to sort per-coach/watcher EA reminders b/c TreeSet
uses the specified Comparator to determine both ordinal
and equality relationships between elements in the collection.
So if two objects have the same ordinal relationship they're
considered equivalent and one is dropped out of the Set. This
was problematic in this particular case because the
Comparator that was being used only compared EA reminder by
EA creation/response dates. So given two EAs with the same creation/
response date, only one would be successfully added to the
collection, resulting in a potentially *much* smaller overall
collection size than one might expect.