Quicksand - make page object notifications work properly with quicksand

Summary: Fixes T7680. Make it so the listen behavior can be initialized multiple times from the server by having the behavior only update a few static data variables on subsequent initializations.

Test Plan:
visited TX with user A and left a comment with user B and got the "reload" and "TX updated" bubbles.
Reloaded and navigated to /maniphest/ with user A and had user B leave another comment on TX - no "reload" bubble and correct "TX updated" bubble.
Navigated to TX again with user A and had user B leave a comment and got the "reload" and "TX updated" bubbles.
visited TX with user A and left a comment with user B and got the "reload" and "TX updated" bubbles. navigated away with user A and the "reload" bubble was automagically closed.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7680

Differential Revision: https://secure.phabricator.com/D12448