Check for calendar before settings status

Summary:
We should not show the status line in the people hover card
if the calendar app has been uninstalled or is not available for the
current user.

Test Plan:
View hover card with calendar installed and uninstalled.
Make sure I see the status at the correct time.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, chad, Korvin

Maniphest Tasks: T5370

Differential Revision: https://secure.phabricator.com/D9577