Remove deprecated DSA host key from Docker Container (#21522)

Since OpenSSH 7.0 and greater similarly disable the ssh-dss (DSA) public
key algorithm, and recommend against its use.
http://www.openssh.com/legacy.html

## :warning: BREAKING :warning:

This patch will remove DSA host key form OpenSSH daemon configuration
file.

Signed-off-by: baronbunny <its@baronbunny.cn>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

docker/root/etc/s6/openssh/setup

@@ -14,11 +14,6 @@ if [ ! -f /data/ssh/ssh_host_rsa_key ]; then
     ssh-keygen -t rsa -b 2048 -f /data/ssh/ssh_host_rsa_key -N "" > /dev/null
 fi
 
-if [ ! -f /data/ssh/ssh_host_dsa_key ]; then
-    echo "Generating /data/ssh/ssh_host_dsa_key..."
-    ssh-keygen -t dsa -f /data/ssh/ssh_host_dsa_key -N "" > /dev/null
-fi
-
 if [ ! -f /data/ssh/ssh_host_ecdsa_key ]; then
     echo "Generating /data/ssh/ssh_host_ecdsa_key..."
     ssh-keygen -t ecdsa -b 256 -f /data/ssh/ssh_host_ecdsa_key -N "" > /dev/null
@@ -36,17 +31,12 @@ if [ -e /data/ssh/ssh_host_ecdsa_cert ]; then
   SSH_ECDSA_CERT=${SSH_ECDSA_CERT:-"/data/ssh/ssh_host_ecdsa_cert"}
 fi
 
-if [ -e /data/ssh/ssh_host_dsa_cert ]; then
-  SSH_DSA_CERT=${SSH_DSA_CERT:-"/data/ssh/ssh_host_dsa_cert"}
-fi
-
 if [ -d /etc/ssh ]; then
     SSH_PORT=${SSH_PORT:-"22"} \
     SSH_LISTEN_PORT=${SSH_LISTEN_PORT:-"${SSH_PORT}"} \
     SSH_ED25519_CERT="${SSH_ED25519_CERT:+"HostCertificate "}${SSH_ED25519_CERT}" \
     SSH_RSA_CERT="${SSH_RSA_CERT:+"HostCertificate "}${SSH_RSA_CERT}" \
     SSH_ECDSA_CERT="${SSH_ECDSA_CERT:+"HostCertificate "}${SSH_ECDSA_CERT}" \
-    SSH_DSA_CERT="${SSH_DSA_CERT:+"HostCertificate "}${SSH_DSA_CERT}" \
     SSH_MAX_STARTUPS="${SSH_MAX_STARTUPS:+"MaxStartups "}${SSH_MAX_STARTUPS}" \
     SSH_MAX_SESSIONS="${SSH_MAX_SESSIONS:+"MaxSessions "}${SSH_MAX_SESSIONS}" \
     SSH_INCLUDE_FILE="${SSH_INCLUDE_FILE:+"Include "}${SSH_INCLUDE_FILE}" \

docker/root/etc/templates/sshd_config

@@ -16,8 +16,6 @@ HostKey /data/ssh/ssh_host_rsa_key
 ${SSH_RSA_CERT}
 HostKey /data/ssh/ssh_host_ecdsa_key
 ${SSH_ECDSA_CERT}
-HostKey /data/ssh/ssh_host_dsa_key
-${SSH_DSA_CERT}
 
 AuthorizedKeysFile .ssh/authorized_keys
 AuthorizedPrincipalsFile .ssh/authorized_principals