Coverity analysis defect 16045: Inequality comparison against NULL

A new defect has been detected and assigned to spencer in Coverity Connect.
http://coverity.mongodb.com//sourcebrowser.htm?projectId=10001#mergedDefectId=16045
The defect was flagged by checker BAD_COMPARE in
file /src/mongo/db/auth/authz_manager_external_state_mock.cpp
function mongo::AuthzManagerExternalStateMock::getStoredAuthorizationVersion(int *)
and this ticket was created by asya