Correct "getActiveBindings()" method name

Summary: This method was incorrectly renamed by D21628. See https://discourse.phabricator-community.org/t/unable-to-lease-host/4696.

Test Plan: Looked at it, will deploy etc.

Subscribers: yelirekim, PHID-OPKG-gm6ozazyms6q6i22gyam

Differential Revision: https://secure.phabricator.com/D21644