libbsm: honour AU_OFLAG_NORESOLVE

AU_OFLAG_NORESOLVE is documented as "Leave user and group IDs in their
numeric form" but it was not actually tested.

OpenBSM pull request at https://github.com/openbsm/openbsm/pull/85

PR: 282271
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D47263

(cherry picked from commit ba10bfe509dcb5d408de89c886527035068b8f17)
(cherry picked from commit 914752d0f7f874ab4fc8393aee28c22df87324f2)