pfkey_dump_sadb: when it get an error using sysctl, mimic an error msg from keysock so that caller can process it correctly.
pfkey_dump_sadb: when it get an error using sysctl,
mimic an error msg from keysock so that caller can process it correctly.

NetBSD PR/23122.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame