libapparmor: Preserve errno across aa_*_unref() functions
Callers of aa_features_unref(), aa_kernel_interface_unref(), and aa_policy_cache_unref() had to store off errno and restore it after calling those functions in error paths. This patch preserves errno across those *_unref() functions so that callers don't have to.
Signed-off-by: Tyler Hicks tyhicks@canonical.com