rP944b257d5df3

Fix a policy issue where permissions were not properly checked when disabling global builtin queries

Summary: See <https://hackerone.com/reports/1573143>. The pathway for disabling global builtin queries is missing a policy check. Add it.

Test Plan:
- Accessed the "/search/delete/id/.../" URI for a global builtin query as a non-administrator.
- Before patch: could improperly disable queries.
-After patch: proper policy exception.

Differential Revision: https://secure.phabricator.com/D21851