tests: set PerSourcePenalties for sshd, bump debug level to 2

To silence a warning, in rare failure cases:
```
srclimit_penalise: ipv4: new 172.17.0.1/32 deferred penalty of 1.000
  seconds for penalty: connections without attempting authentication
```
Ref: https://github.com/libssh2/libssh2/actions/runs/37207427612/job/111451438515?pr=2649#step:25:537

Also:
- seize the opportunity and bump sshd debug level to 2.
  Level 1 is too low to see clearly in some cases.
  Ref: https://github.com/libssh2/libssh2/pull/2649
  Follow-up to 45aa5c5fa4 #2621

Refs:
https://man.openbsd.org/sshd_config#PerSourcePenalties
https://www.openssh.org/txt/release-9.8

Closes #2650

tests/openssh_server/Dockerfile

@@ -63,6 +63,7 @@ RUN echo 'HostCertificate /etc/ssh/ssh_host_rsa_key-cert.pub' >> /etc/ssh/sshd_c
 RUN echo 'HostCertificate /etc/ssh/ssh_host_ecdsa_key-cert.pub' >> /etc/ssh/sshd_config
 RUN echo 'HostCertificate /etc/ssh/ssh_host_ed25519_key-cert.pub' >> /etc/ssh/sshd_config
 RUN echo 'HostCertificate /etc/ssh/ssh_host_mldsa44-ed25519_key-cert.pub' >> /etc/ssh/sshd_config
+RUN echo 'PerSourcePenalties no' >> /etc/ssh/sshd_config
 
 # SSH login fix. Otherwise user is kicked off after login
 RUN sed 's/session\s*required\s*pam_loginuid.so/session optional pam_loginuid.so/g' -i /etc/pam.d/sshd

tests/openssh_server/sshd_config

@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
-LogLevel DEBUG1
+LogLevel DEBUG2
 
 CASignatureAlgorithms +ssh-rsa
 HostKeyAlgorithms +ssh-rsa,ssh-rsa-cert-v01@openssh.com