openbsd: Fix usbi_sanitize_device error handling

If usbi_sanitize_device fails we need to continue from the beginning of
the loop, rather then going on with the device we've just free-ed.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
openbsd: Fix a memleak

discovered_devs_append takes a reference to the past in dev, so we must
release our own reference.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Make usbi_get_device_by_session_id return a ref to the found device

Signed-off-by: Hans de Goede <hdegoede@redhat.com>