Increase RTR PDU limit to 48k and limit number of SPAS to 10'000.

Increase RTR PDU limit to 48k and limit number of SPAS to 10'000.

PDU larger then 48k will result in a session reset while ASPA records
with more than 10'000 entries will be implicitly withdrawn.

Also truncate RTR error PDUs to only include 256 bytes of the faulty PDU.
It makes no sense to include more to identify the issue.
OK tb@