Fix calendar part 2

Summary: D8341 was a good start. However, I was looping through all the statuses each time, when I should only deal with a given status once. Instead, unset() a status from the list of statuses once we handled it. Also, delete the last old $key thing, which interfered with my chosen strategy.

Test Plan: made a two day event and verified it showed up in just those two days. (will push and test again just in case but this should be it)

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8342