Bug#959206: sshd: kex_exchange_identification failures are logged as error

[Christian Göttsche <cgzones@googlemail.com>]

Package: openssh-server
Version: 1:8.2p1-4

I am running sshd on a custom port and a few bots/spammers are trying
to connect.
This lead to messages like:

sshd[197482]: error: kex_exchange_identification: Connection closed by
remote host
sshd[205072]: error: kex_exchange_identification: banner line contains
invalid characters
sshd[1012348]: error: kex_exchange_identification: client sent invalid
protocol identifier "GET / HTTP/1.1"

Since these events are non-critical and remotely trigger-able, can the
severity of these log entries be lowered from error to warning?

Best regards
     Christian Göttsche