When working on Linux emulation on FreeBSD, I assumed that
SpecGenerator.ImageOS was always populated from the image's OS value but
in fact, this value comes from the CLI --os flag if set, otherwise "".
This broke running FreeBSD native containers unless --os=freebsd was
also set. Fix the problem by getting the value from the image itself.
This is a strong incentive for me to complete a stalled project to enable
podman system tests on FreeBSD.
[NO NEW TESTS NEEDED]
Signed-off-by: Doug Rabson <dfr@rabson.org>
644f7cd9be