Exclude disabled (disapproved) users from count on People application on homepage

Summary:
The People application shows users awaiting approval, but incorrectly counts disabled users (i.e., users who were not approved).

Instead, count only non-disabled, non-approved users.

Test Plan: My homepage count dropped from 4 to 1, corresponding to the actual number of accounts.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, spicyj

Differential Revision: https://secure.phabricator.com/D8486