Back off on generating noise in the event of a PING frame

Back off on generating noise in the event of a PING frame

If either endpoint issues a PING frame while we are introducing noise
into the communication then there is a danger that the connection itself
will fail. We detect the PING and then back off on generating noise for a
short while. It should be sufficient to just ensure that the next datagram
does not get dropped for each endpoint.

Fixes #22199

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22243)